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Ca 2+ ‐dependent conformational changes in bovine GCAP‐2
Author(s) -
Hughes Robert E.,
Hurley James B.,
Brzovic Peter S.,
Dizhoor Alexander M.,
Klevit Rachel E.
Publication year - 1998
Publication title -
protein science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.353
H-Index - 175
eISSN - 1469-896X
pISSN - 0961-8368
DOI - 10.1002/pro.5560071222
Subject(s) - chemistry , biophysics , physics , crystallography , biology
GCAP‐2, a mammalian photoreceptor‐specific protein, is a Ca 2+ ‐dependent regulator of the retinal membrane guanylyl cyclases (Ret‐GCs). Sensing the fall in intracellular free Ca 2+ after photo‐excitation, GCAP‐2 stimulates the activity of Ret‐GC leading to cGMP production. Like other members of the recoverin superfamily, GCAP‐2 is a small N‐myristoylated protein containing four EF‐hand consensus motifs. In this study, we demonstrate that like recoverin and neurocalcin, GCAP‐2 alters its conformation in response to Ca 2+ ‐binding as measured by a Ca 2+ ‐dependent change in its far UV CD spectrum. Differences in the conformation of the Ca 2+ ‐bound and Ca 2+ ‐free forms of GCAP‐2 were also observed by examining their relative susceptibility to V8 protease. In contrast to recoverin, we do not observe proteolytic cleavage of the myristoylated N‐terminus of Ca 2+ ‐bound GCAP‐2. NMR spectra also show that, in contrast to recoverin, the chemical environment of the N‐terminus of GCAP‐2 is not dramatically altered by Ca 2+ binding. Despite the similarity of GCAP‐2 and recoverin, the structural consequences of Ca 2+ ‐binding for these two proteins are significantly dissimilar.