J. Biol. Chem., Vol. 255, Issue 21, 10060-10063, 11, 1980
Amino acid sequence of the signal peptide of apoVLDL-II, a major apoprotein in avian very low density lipoproteins
L Chan, WA Bradley and AR Means
ApoVLDL-II is a major apoprotein in avian very low density lipoproteins
(Jackson, R. L., Lin, H.-Y., Chan, L., and Means, A.R. (1977) J. Biol.
Chem. 252, 250-253). Partially purified apoVLDL-II mRNA was translated in
vitro in a wheat germ system in the presence of various labeled amino
acids. The product, designated preapoVLDL-II, was purified by
immunoprecipitation and sodium dodecyl sulfate acrylamide gel
electrophoresis. It was subjected to automated Edman degradation in a
Beckman Sequencer. The signal peptide was found to be a 23-amino acid
NH2-terminal extension of the mature protein with the following sequence:
Met-Gln-Tyr-Arg-Ala-Leu-Val-Ile-Ala-Val-Ile-Leu-Leu-Leu-Ser-
Thr-Val-Pro-Glu-Val-Cys-Ser-Lys where Lys is the NH2-terminal residue of
mature apoVLDL-II. The abundance and distribution of the hydrophobic amino
acid residues are very similar to those of other signal sequences and the
average hydrophobicity for the 23 residues is -1227 cal/mol/residue.
However, translocation of preapoVLDL-II would represent a unique case of
vectorial migration of a protein through a membrane since apoVLDL-II is
itself an apolipoprotein and binds lipid spontaneously.
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