HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Ewart, K. V. Articles by Hew, C. L. Search for Related Content PubMed PubMed Citation Articles by Ewart, K. V. Articles by Hew, C. L. Social Bookmarking                      What's this?

Volume 271, Number 28, Issue of July 12, 1996 pp. 16627-16632
©1996 by The American Society for Biochemistry and Molecular Biology, Inc.

---

Ca²⁺-dependent Antifreeze Proteins
MODULATION OF CONFORMATION AND ACTIVITY BY DIVALENT METAL IONS

(Received for publication, February 21, 1996, and in revised form, April 19, 1996)

K. Vanya Ewart , Daniel S. C. Yang ^¶ , Vettai S. Ananthanarayanan ^¶ , Garth L. Fletcher and Choy L. Hew

From the  Research Institute, Hospital for Sick Children, Toronto, and Departments of Clinical Biochemistry and Biochemistry, University of Toronto, Toronto, Ontario, Canada M5G 1L5, the ^¶ Department of Biochemistry, McMaster University, Hamilton, Ontario, Canada L8N 3Z5, and the  Ocean Sciences Center and Department of Biology, Memorial University of Newfoundland, St. John's, Newfoundland, Canada A1C 5S7

The antifreeze proteins (AFPs) are structurally diverse molecules that share an ability to bind to ice crystals and inhibit their growth. The type II fish AFPs of Atlantic herring and smelt are unique among known AFPs in their requirement of a cofactor for antifreeze activity. These AFPs are homologous with the carbohydrate-recognition domains of Ca²⁺-dependent (C-type) lectins and require Ca²⁺ for their activity. To investigate the role of metal ions in the structure and function of type II AFPs, the binding of Ca²⁺ and other divalent cations to herring AFP was investigated. Binding studies using ⁴⁵Ca²⁺ demonstrated that the AFP has a single Ca²⁺-binding site with a K_d of 9 µM. Proteolysis protection studies and measurement of antifreeze activity revealed a conformational change from a protease-sensitive and inactive apoAFP to a protease-resistant active AFP upon Ca²⁺ binding. Other divalent metal ions including Mn²⁺, Ba²⁺, and Zn²⁺ bind at the Ca²⁺-binding site and induce a similar change. A saturatable increase in tryptophan emission intensity at 340 nm also occurred upon Ca²⁺ addition. Whereas antifreeze activity appeared normal when Ca²⁺ or Mn²⁺ were bound, it was much lower in the presence of other metal ions. When Ba²⁺ was bound to the AFP, ice crystals showed a distinct difference in morphology. These studies demonstrate that herring AFP specifically binds Ca²⁺ and, consequently, adopts a conformation that is essential for its ice-binding activity.

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

This article has been cited by other articles:

				C. S. Strom, X. Y. Liu, and Z. Jia Antifreeze Protein-induced Morphological Modification Mechanisms Linked to Ice Binding Surface J. Biol. Chem., July 30, 2004; 279(31): 32407 - 32417. [Abstract] [Full Text] [PDF]

				M. Stressmann, S. Kitao, M. Griffith, C. Moresoli, L. A. Bravo, and A. G. Marangoni Calcium Interacts with Antifreeze Proteins and Chitinase from Cold-Acclimated Winter Rye Plant Physiology, May 1, 2004; 135(1): 364 - 376. [Abstract] [Full Text] [PDF]

				Y. Cheng, Z. Yang, H. Tan, R. Liu, G. Chen, and Z. Jia Analysis of Ice-Binding Sites in Fish Type II Antifreeze Protein by Quantum Mechanics Biophys. J., October 1, 2002; 83(4): 2202 - 2210. [Abstract] [Full Text] [PDF]

				P. Hogger, J. Dreier, A. Droste, F. Buck, and C. Sorg Identification of the Integral Membrane Protein RM3/1 on Human Monocytes as a Glucocorticoid-Inducible Member of the Scavenger Receptor Cysteine-Rich Family (CD163) J. Immunol., August 15, 1998; 161(4): 1883 - 1890. [Abstract] [Full Text] [PDF]

				N. P. Mullin, P. G. Hitchen, and M. E. Taylor Mechanism of Ca2+ and Monosaccharide Binding to a C-type Carbohydrate-recognition Domain of the Macrophage Mannose Receptor J. Biol. Chem., February 28, 1997; 272(9): 5668 - 5681. [Abstract] [Full Text] [PDF]