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Calmodulin binding to α 1 ‐purothionin: Soloution binding and modeling of the complex
Author(s) -
Rao Usha,
Teeter Martha M.,
EricksonViitanen Susan,
DeGrado William F.
Publication year - 1992
Publication title -
proteins: structure, function, and bioinformatics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.699
H-Index - 191
eISSN - 1097-0134
pISSN - 0887-3585
DOI - 10.1002/prot.340140202
Subject(s) - calmodulin , chemistry , binding site , crystallography , stereochemistry , molecular model , molecule , helix (gastropod) , binding pocket , biophysics , biochemistry , biology , ecology , organic chemistry , snail , enzyme
CD and fluorescence spectroscopic measurements show that calmodulin (CaM) binds to purothionins (alpha; 1 ‐purothionin: α 1 ‐PT; β‐purothionin: β‐PT) in 1:1 stoichiometry with an affinity similar to that exhibited with the tightest binding CaM‐binding peptides. Using the available crystal structures of CaM and α 1 ‐PT, a model has been built for the interaction of CaM and α 1 ‐PT and subjected to potential energy minimization. In the model, there is a bend in the central helix of CaM similar to that suggested by Persechini and Kretsinger (J. Card. Pharm. 12:501–512, 1988). α 1 ‐PT fits snugly into the cavity formed by the bent CaM molecule with each of its two helices making apolar interactions with each of the two hydrophobic clefts situated at the terminal domains of CaM. The complex is further stabilized by numerous polar and electrostatic interactions on the rims of the clefts. Our model is compared with two other similar models previously re‐ported for the CaM complexes with other helical peptides and generalizations about the mode of CaM binding to target proteins are made, which have wide relevance to the function of CaM. By analogy, a similar model is pre‐dicted for a CaM–β‐PT complex. © 1992 Wiley‐Liss, Inc.