JBC Avanti Polar Lipids

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
 QUICK SEARCH:   [advanced]


     


This Article
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Cruz, J. C.
Right arrow Articles by Chang, T.-Y.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Cruz, J. C.
Right arrow Articles by Chang, T.-Y.
Social Bookmarking
 Add to CiteULike   Add to Complore   Add to Connotea   Add to Del.icio.us   Add to Digg   Add to Reddit   Add to Technorati  
What's this?

J Biol Chem, Vol. 275, Issue 6, 4013-4021, February 11, 2000

Role of Niemann-Pick Type C1 Protein in Intracellular Trafficking of Low Density Lipoprotein-derived Cholesterol*

Jonathan C. Cruz, Shigeki Sugii, Chunjiang Yu, and Ta-Yuan ChangDagger

From the Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03755

Niemann-Pick type C (NPC) is a disease that affects intracellular cholesterol-trafficking pathways. By cloning the hamster ortholog of NPC1, we identified the molecular lesions in two independently isolated Chinese hamster ovary cell mutants, CT60 and CT43. Both mutants lead to premature translational terminations of the NPC1 protein. Transfecting hamster NPC1 cDNA complemented the defects of the mutants. Investigation of the CT mutants, their parental cells, and an NPC1-stable transfectant allow us to present evidence that NPC1 is involved in a post-plasma membrane cholesterol-trafficking pathway. We found that the initial movement of low density lipoprotein (LDL)-derived cholesterol to the plasma membrane (PM) did not require NPC1. After reaching the PM and subsequent internalization, however, cholesterol trafficking back to the PM did involve NPC1. Both LDL-derived cholesterol and cholesterol originating from the PM accumulated in a dense, intracellular compartment in the CT mutants. Cholesterol movement from this compartment to the PM or endoplasmic reticulum was defective in the CT mutants. Our results functionally distinguish the dense, intracellular compartment from the early endocytic hydrolytic organelle and imply that NPC1 is involved in sorting cholesterol from the intracellular compartment back to the PM or to the endoplasmic reticulum.


* This work was supported by National Institutes of Health Grant HL36709 (to T. Y. C.).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

The nucleotide sequence(s) reported in this paper has been submitted to the GenBankTM/EMBL Data Bank with accession number(s) AF182744.

Dagger To whom correspondence should be addressed. Tel.: 603-650-1622; Fax: 603-650-1128; E-mail: Ta.Yuan.Chang@Dartmouth.edu.


Copyright © 2000 by The American Society for Biochemistry and Molecular Biology, Inc.

Add to CiteULike CiteULike   Add to Complore Complore   Add to Connotea Connotea   Add to Del.icio.us Del.icio.us   Add to Digg Digg   Add to Reddit Reddit   Add to Technorati Technorati    What's this?


This article has been cited by other articles:


Home page
J. Biol. Chem.Home page
Y. Yamauchi, P. C. Reid, J. B. Sperry, K. Furukawa, M. Takeya, C. C. Y. Chang, and T.-Y. Chang
Plasma Membrane Rafts Complete Cholesterol Synthesis by Participating in Retrograde Movement of Precursor Sterols
J. Biol. Chem., November 30, 2007; 282(48): 34994 - 35004.
[Abstract] [Full Text] [PDF]


Home page
CirculationHome page
C. L. Welch, Y. Sun, B. J. Arey, V. Lemaitre, N. Sharma, M. Ishibashi, S. Sayers, R. Li, A. Gorelik, N. Pleskac, et al.
Spontaneous Atherothrombosis and Medial Degradation in Apoe / , Npc1 / Mice
Circulation, November 20, 2007; 116(21): 2444 - 2452.
[Abstract] [Full Text] [PDF]


Home page
J. Cell Sci.Home page
A. C. Berger, G. Salazar, M. L. Styers, K. A. Newell-Litwa, E. Werner, R. A. Maue, A. H. Corbett, and V. Faundez
The subcellular localization of the Niemann-Pick Type C proteins depends on the adaptor complex AP-3
J. Cell Sci., October 15, 2007; 120(20): 3640 - 3652.
[Abstract] [Full Text] [PDF]


Home page
J. Lipid Res.Home page
T. A. Pagler, A. Neuhofer, H. Laggner, W. Strobl, and H. Stangl
Cholesterol efflux via HDL resecretion occurs when cholesterol transport out of the lysosome is impaired
J. Lipid Res., October 1, 2007; 48(10): 2141 - 2150.
[Abstract] [Full Text] [PDF]


Home page
J. Biol. Chem.Home page
S. R. Cheruku, Z. Xu, R. Dutia, P. Lobel, and J. Storch
Mechanism of Cholesterol Transfer from the Niemann-Pick Type C2 Protein to Model Membranes Supports a Role in Lysosomal Cholesterol Transport
J. Biol. Chem., October 20, 2006; 281(42): 31594 - 31604.
[Abstract] [Full Text] [PDF]


Home page
J. Biol. Chem.Home page
S. Sugii, S. Lin, N. Ohgami, M. Ohashi, C. C. Y. Chang, and T.-Y. Chang
Roles of Endogenously Synthesized Sterols in the Endocytic Pathway
J. Biol. Chem., August 11, 2006; 281(32): 23191 - 23206.
[Abstract] [Full Text] [PDF]


Home page
J. Immunol.Home page
Y. Sagiv, K. Hudspeth, J. Mattner, N. Schrantz, R. K. Stern, D. Zhou, P. B. Savage, L. Teyton, and A. Bendelac
Cutting Edge: Impaired Glycosphingolipid Trafficking and NKT Cell Development in Mice Lacking Niemann-Pick Type C1 Protein
J. Immunol., July 1, 2006; 177(1): 26 - 30.
[Abstract] [Full Text] [PDF]


Home page
J. Lipid Res.Home page
B. Karten, R. B. Campenot, D. E. Vance, and J. E. Vance
The Niemann-Pick C1 protein in recycling endosomes of presynaptic nerve terminals
J. Lipid Res., March 1, 2006; 47(3): 504 - 514.
[Abstract] [Full Text] [PDF]


Home page
J. Lipid Res.Home page
N. H. Pipalia, A. Huang, H. Ralph, M. Rujoi, and F. R. Maxfield
Automated microscopy screening for compounds that partially revert cholesterol accumulation in Niemann-Pick C cells
J. Lipid Res., February 1, 2006; 47(2): 284 - 301.
[Abstract] [Full Text] [PDF]


Home page
Stem CellsHome page
S.-R. Yang, S.-J. Kim, K.-H. Byun, B. Hutchinson, B.-H. Lee, M. Michikawa, Y.-S. Lee, and K.-S. Kang
NPC1 Gene Deficiency Leads to Lack of Neural Stem Cell Self-Renewal and Abnormal Differentiation Through Activation of p38 Mitogen-Activated Protein Kinase Signaling
Stem Cells, February 1, 2006; 24(2): 292 - 298.
[Abstract] [Full Text] [PDF]


Home page
J. Lipid Res.Home page
J. A. Maguire and J. W. Reagan Jr.
Silencing of the mutant SCAP allele accounts for restoration of a normal phenotype in CT60 cells selected for NPC1 expression
J. Lipid Res., September 1, 2005; 46(9): 1840 - 1848.
[Abstract] [Full Text] [PDF]


Home page
J. Biol. Chem.Home page
E. E. Millard, S. E. Gale, N. Dudley, J. Zhang, J. E. Schaffer, and D. S. Ory
The Sterol-sensing Domain of the Niemann-Pick C1 (NPC1) Protein Regulates Trafficking of Low Density Lipoprotein Cholesterol
J. Biol. Chem., August 5, 2005; 280(31): 28581 - 28590.
[Abstract] [Full Text] [PDF]


Home page
J. Biol. Chem.Home page
H. Zheng, R. S. Kiss, V. Franklin, M.-D. Wang, B. Haidar, and Y. L. Marcel
ApoA-I Lipidation in Primary Mouse Hepatocytes: SEPARATE CONTROLS FOR PHOSPHOLIPID AND CHOLESTEROL TRANSFERS
J. Biol. Chem., June 3, 2005; 280(22): 21612 - 21621.
[Abstract] [Full Text] [PDF]


Home page
Proc. Natl. Acad. Sci. USAHome page
N. Ohgami, D. C. Ko, M. Thomas, M. P. Scott, C. C. Y. Chang, and T.-Y. Chang
Binding between the Niemann-Pick C1 protein and a photoactivatable cholesterol analog requires a functional sterol-sensing domain
PNAS, August 24, 2004; 101(34): 12473 - 12478.
[Abstract] [Full Text] [PDF]


Home page
Arterioscler. Thromb. Vasc. Bio.Home page
R. E. Soccio and J. L. Breslow
Intracellular Cholesterol Transport
Arterioscler. Thromb. Vasc. Biol., July 1, 2004; 24(7): 1150 - 1160.
[Abstract] [Full Text] [PDF]


Home page
J. Biol. Chem.Home page
T. Kishida, I. Kostetskii, Z. Zhang, F. Martinez, P. Liu, S. U. Walkley, N. K. Dwyer, E. J. Blanchette-Mackie, G. L. Radice, and J. F. Strauss III
Targeted Mutation of the MLN64 START Domain Causes Only Modest Alterations in Cellular Sterol Metabolism
J. Biol. Chem., April 30, 2004; 279(18): 19276 - 19285.
[Abstract] [Full Text] [PDF]


Home page
J. Biol. Chem.Home page
R. Salvioli, S. Scarpa, F. Ciaffoni, M. Tatti, C. Ramoni, M. T. Vanier, and A. M. Vaccaro
Glucosylceramidase Mass and Subcellular Localization Are Modulated by Cholesterol in Niemann-Pick Disease Type C
J. Biol. Chem., April 23, 2004; 279(17): 17674 - 17680.
[Abstract] [Full Text] [PDF]


Home page
J. Cell Biol.Home page
K. Malathi, K. Higaki, A. H. Tinkelenberg, D. A. Balderes, D. Almanzar-Paramio, L. J. Wilcox, N. Erdeniz, F. Redican, M. Padamsee, Y. Liu, et al.
Mutagenesis of the putative sterol-sensing domain of yeast Niemann Pick C-related protein reveals a primordial role in subcellular sphingolipid distribution
J. Cell Biol., February 16, 2004; 164(4): 547 - 556.
[Abstract] [Full Text] [PDF]


Home page
J. Lipid Res.Home page
A. Umeda, H. Fujita, T. Kuronita, K. Hirosako, M. Himeno, and Y. Tanaka
Distribution and trafficking of MPR300 is normal in cells with cholesterol accumulated in late endocytic compartments: evidence for early endosome-to-TGN trafficking of MPR300
J. Lipid Res., October 1, 2003; 44(10): 1821 - 1832.
[Abstract] [Full Text] [PDF]


Home page
J. Biol. Chem.Home page
S. Sugii, P. C. Reid, N. Ohgami, H. Du, and T.-Y. Chang
Distinct Endosomal Compartments in Early Trafficking of Low Density Lipoprotein-derived Cholesterol
J. Biol. Chem., July 11, 2003; 278(29): 27180 - 27189.
[Abstract] [Full Text] [PDF]


Home page
J. Lipid Res.Home page
S. Sugii, P. C. Reid, N. Ohgami, Y. Shimada, R. A. Maue, H. Ninomiya, Y. Ohno-Iwashita, and T.-Y. Chang
Biotinylated {theta}-toxin derivative as a probe to examine intracellular cholesterol-rich domains in normal and Niemann-Pick type C1 cells
J. Lipid Res., May 1, 2003; 44(5): 1033 - 1041.
[Abstract] [Full Text] [PDF]


Home page
J. Lipid Res.Home page
P. C. Reid, S. Sugii, and T.-Y. Chang
Trafficking defects in endogenously synthesized cholesterol in fibroblasts, macrophages, hepatocytes, and glial cells from Niemann-Pick type C1 mice
J. Lipid Res., May 1, 2003; 44(5): 1010 - 1019.
[Abstract] [Full Text] [PDF]


Home page
J. Biol. Chem.Home page
K. M. Wojtanik and L. Liscum
The Transport of Low Density Lipoprotein-derived Cholesterol to the Plasma Membrane Is Defective in NPC1 Cells
J. Biol. Chem., April 18, 2003; 278(17): 14850 - 14856.
[Abstract] [Full Text] [PDF]


Home page
J. Biol. Chem.Home page
B. Karten, D. E. Vance, R. B. Campenot, and J. E. Vance
Trafficking of Cholesterol from Cell Bodies to Distal Axons in Niemann Pick C1-deficient Neurons
J. Biol. Chem., January 31, 2003; 278(6): 4168 - 4175.
[Abstract] [Full Text] [PDF]


Home page
J. Lipid Res.Home page
P. Tarugi, G. Ballarini, B. Bembi, C. Battisti, S. Palmeri, F. Panzani, E. Di Leo, C. Martini, A. Federico, and S. Calandra
Niemann-Pick type C disease: mutations of NPC1 gene and evidence of abnormal expression of some mutant alleles in fibroblasts
J. Lipid Res., November 1, 2002; 43(11): 1908 - 1919.
[Abstract] [Full Text] [PDF]


Home page
Mol. Biol. CellHome page
M. Holtta-Vuori, K. Tanhuanpaa, W. Mobius, P. Somerharju, and E. Ikonen
Modulation of Cellular Cholesterol Transport and Homeostasis by Rab11
Mol. Biol. Cell, September 1, 2002; 13(9): 3107 - 3122.
[Abstract] [Full Text] [PDF]


Home page
J. Lipid Res.Home page
J. C. Cruz, M. Thomas, E. Wong, N. Ohgami, S. Sugii, T. Curphey, C. C. Y. Chang, and T.-Y. Chang
Synthesis and biochemical properties of a new photoactivatable cholesterol analog 7,7-azocholestanol and its linoleate ester in Chinese hamster ovary cell lines
J. Lipid Res., August 1, 2002; 43(8): 1341 - 1347.
[Abstract] [Full Text] [PDF]


Home page
J. Lipid Res.Home page
W. S. Garver, K. Krishnan, J. R. Gallagos, M. Michikawa, G. A. Francis, and R. A. Heidenreich
Niemann-Pick C1 protein regulates cholesterol transport to the trans-Golgi network and plasma membrane caveolae
J. Lipid Res., April 1, 2002; 43(4): 579 - 589.
[Abstract] [Full Text] [PDF]


Home page
J. Neurosci.Home page
H. Runz, J. Rietdorf, I. Tomic, M. de Bernard, K. Beyreuther, R. Pepperkok, and T. Hartmann
Inhibition of Intracellular Cholesterol Transport Alters Presenilin Localization and Amyloid Precursor Protein Processing in Neuronal Cells
J. Neurosci., March 1, 2002; 22(5): 1679 - 1689.
[Abstract] [Full Text] [PDF]


Home page
J. Biol. Chem.Home page
A. Frolov, K. Srivastava, D. Daphna-Iken, L. M. Traub, J. E. Schaffer, and D. S. Ory
Cholesterol Overload Promotes Morphogenesis of a Niemann-Pick C (NPC)-like Compartment Independent of Inhibition of NPC1 or HE1/NPC2 Function
J. Biol. Chem., November 30, 2001; 276(49): 46414 - 46421.
[Abstract] [Full Text] [PDF]


Home page
J. Biol. Chem.Home page
W. Chen, Y. Sun, C. Welch, A. Gorelik, A. R. Leventhal, I. Tabas, and A. R. Tall
Preferential ATP-binding Cassette Transporter A1-mediated Cholesterol Efflux from Late Endosomes/Lysosomes
J. Biol. Chem., November 16, 2001; 276(47): 43564 - 43569.
[Abstract] [Full Text] [PDF]


Home page
J. Lipid Res.Home page
H. S. Kruth, I. Ifrim, J. Chang, L. Addadi, D. Perl-Treves, and W.-Y. Zhang
Monoclonal antibody detection of plasma membrane cholesterol microdomains responsive to cholesterol trafficking
J. Lipid Res., September 1, 2001; 42(9): 1492 - 1500.
[Abstract] [Full Text] [PDF]


Home page
Mol. Endocrinol.Home page
B. D. Murphy, E. Lalli, L. P. Walsh, Z. Liu, J. Soh, D. M. Stocco, and P. Sassone-Corsi
Heat Shock Interferes with Steroidogenesis by Reducing Transcription of the Steroidogenic Acute Regulatory Protein Gene
Mol. Endocrinol., August 1, 2001; 15(8): 1255 - 1263.
[Abstract] [Full Text] [PDF]


Home page
J. Lipid Res.Home page
A. Mohammadi, R. J. Perry, M. K. Storey, H. W. Cook, D. M. Byers, and N. D. Ridgway
Golgi localization and phosphorylation of oxysterol binding protein in Niemann-Pick C and U18666A-treated cells
J. Lipid Res., July 1, 2001; 42(7): 1062 - 1071.
[Abstract] [Full Text] [PDF]


Home page
Proc. Natl. Acad. Sci. USAHome page
M. Zhang, N. K. Dwyer, D. C. Love, A. Cooney, M. Comly, E. Neufeld, P. G. Pentchev, E. J. Blanchette-Mackie, and J. A. Hanover
Cessation of rapid late endosomal tubulovesicular trafficking in Niemann-Pick type C1 disease
PNAS, April 10, 2001; 98(8): 4466 - 4471.
[Abstract] [Full Text] [PDF]


Home page
Mol. Biol. CellHome page
D. C. Ko, M. D. Gordon, J. Y. Jin, and M. P. Scott
Dynamic Movements of Organelles Containing Niemann-Pick C1 Protein: NPC1 Involvement in Late Endocytic Events
Mol. Biol. Cell, March 1, 2001; 12(3): 601 - 614.
[Abstract] [Full Text]


Home page
J. Cell Sci.Home page
S Lusa, T. Blom, E. Eskelinen, E Kuismanen, J. Mansson, K Simons, and E Ikonen
Depletion of rafts in late endocytic membranes is controlled by NPC1-dependent recycling of cholesterol to the plasma membrane
J. Cell Sci., January 5, 2001; 114(10): 1893 - 1900.
[Abstract] [PDF]


Home page
Hum Mol GenetHome page
T.-P. Thai, C. Rodemer, A. Jauch, A. Hunziker, A. Moser, K. Gorgas, and W. W. Just
Impaired membrane traffic in defective ether lipid biosynthesis
Hum. Mol. Genet., January 1, 2001; 10(2): 127 - 136.
[Abstract] [Full Text] [PDF]


Home page
ScienceHome page
K. Simons and E. Ikonen
How Cells Handle Cholesterol
Science, December 1, 2000; 290(5497): 1721 - 1726.
[Abstract] [Full Text]


Home page
Arterioscler. Thromb. Vasc. Bio.Home page
Nadia Khelef, T. T. Soe, O. Quehenberger, N. Beatini, I. Tabas, and F. R. Maxfield
Enrichment of Acyl Coenzyme A:Cholesterol O-Acyltransferase Near Trans-Golgi Network and Endocytic Recycling Compartment
Arterioscler. Thromb. Vasc. Biol., July 1, 2000; 20(7): 1769 - 1776.
[Abstract] [Full Text] [PDF]


Home page
J. Biol. Chem.Home page
Y. Lange, J. Ye, M. Rigney, and T. Steck
Cholesterol Movement in Niemann-Pick Type C Cells and in Cells Treated with Amphiphiles
J. Biol. Chem., June 2, 2000; 275(23): 17468 - 17475.
[Abstract] [Full Text] [PDF]


Home page
J. Biol. Chem.Home page
L. P. Henderson, L. Lin, A. Prasad, C. A. Paul, T. Y. Chang, and R. A. Maue
Embryonic Striatal Neurons from Niemann-Pick Type C Mice Exhibit Defects in Cholesterol Metabolism and Neurotrophin Responsiveness
J. Biol. Chem., June 23, 2000; 275(26): 20179 - 20187.
[Abstract] [Full Text] [PDF]


Home page
J. Biol. Chem.Home page
J. P. Davies and Y. A. Ioannou
Topological Analysis of Niemann-Pick C1 Protein Reveals That the Membrane Orientation of the Putative Sterol-sensing Domain Is Identical to Those of 3-Hydroxy-3-methylglutaryl-CoA Reductase and Sterol Regulatory Element Binding Protein Cleavage-activating Protein
J. Biol. Chem., August 4, 2000; 275(32): 24367 - 24374.
[Abstract] [Full Text] [PDF]


Home page
J. Biol. Chem.Home page
E. E. Millard, K. Srivastava, L. M. Traub, J. E. Schaffer, and D. S. Ory
Niemann-Pick Type C1 (NPC1) Overexpression Alters Cellular Cholesterol Homeostasis
J. Biol. Chem., December 1, 2000; 275(49): 38445 - 38451.
[Abstract] [Full Text] [PDF]


Home page
J. Biol. Chem.Home page
J. W. Reagan Jr., M. L. Hubbert, and G. S. Shelness
Posttranslational Regulation of Acid Sphingomyelinase in Niemann-Pick Type C1 Fibroblasts and Free Cholesterol-enriched Chinese Hamster Ovary Cells
J. Biol. Chem., November 22, 2000; 275(48): 38104 - 38110.
[Abstract] [Full Text] [PDF]


Home page
J. Biol. Chem.Home page
M. Zhang, N. K. Dwyer, E. B. Neufeld, D. C. Love, A. Cooney, M. Comly, S. Patel, H. Watari, J. F. Strauss III, P. G. Pentchev, et al.
Sterol-modulated Glycolipid Sorting Occurs in Niemann-Pick C1 Late Endosomes
J. Biol. Chem., January 26, 2001; 276(5): 3417 - 3425.
[Abstract] [Full Text] [PDF]


Home page
J. Biol. Chem.Home page
F. Alpy, M.-E. Stoeckel, A. Dierich, J.-M. Escola, C. Wendling, M.-P. Chenard, M. T. Vanier, J. Gruenberg, C. Tomasetto, and M.-C. Rio
The Steroidogenic Acute Regulatory Protein Homolog MLN64, a Late Endosomal Cholesterol-binding Protein
J. Biol. Chem., February 2, 2001; 276(6): 4261 - 4269.
[Abstract] [Full Text] [PDF]


Home page
J. Biol. Chem.Home page
J. C. Cruz and T.-Y. Chang
Fate of Endogenously Synthesized Cholesterol in Niemann-Pick Type C1 Cells
J. Biol. Chem., December 22, 2000; 275(52): 41309 - 41316.
[Abstract] [Full Text] [PDF]


Home page
J. Biol. Chem.Home page
T. Yamazaki, T.-Y. Chang, C. Haass, and Y. Ihara
Accumulation and Aggregation of Amyloid beta -Protein in Late Endosomes of Niemann-Pick Type C Cells
J. Biol. Chem., February 2, 2001; 276(6): 4454 - 4460.
[Abstract] [Full Text] [PDF]


Home page
J. Biol. Chem.Home page
N. Sawamura, J.-S. Gong, W. S. Garver, R. A. Heidenreich, H. Ninomiya, K. Ohno, K. Yanagisawa, and M. Michikawa
Site-specific Phosphorylation of Tau Accompanied by Activation of Mitogen-activated Protein Kinase (MAPK) in Brains of Niemann-Pick Type C Mice
J. Biol. Chem., March 23, 2001; 276(13): 10314 - 10319.
[Abstract] [Full Text] [PDF]


Home page
J. Biol. Chem.Home page
A. R. Leventhal, W. Chen, A. R. Tall, and I. Tabas
Acid Sphingomyelinase-deficient Macrophages Have Defective Cholesterol Trafficking and Efflux
J. Biol. Chem., November 21, 2001; 276(48): 44976 - 44983.
[Abstract] [Full Text] [PDF]




HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
 All ASBMB Journals   Molecular and Cellular Proteomics 
 Journal of Lipid Research   ASBMB Today 
Copyright © 2000 by the American Society for Biochemistry and Molecular Biology.