A series of point mutations reveal interactions between the calcium-binding sites of calmodulin - PubMed (original) (raw)

Comparative Study

A series of point mutations reveal interactions between the calcium-binding sites of calmodulin

M A Starovasnik et al. Protein Sci. 1992 Feb.

Free PMC article

Abstract

Calmodulin is a member of the "EF-hand" family of Ca(2+)-binding proteins. It consists of two homologous globular domains, each containing two helix-loop-helix Ca(2+)-binding sites. To examine the contribution of individual Ca(2+)-binding sites to the Ca(2+)-binding properties of CaM, a series of four site-directed mutants has been studied. In each, the glutamic acid at position 12 in one of the four Ca(2+)-binding loops has been changed to a glutamine. One-dimensional 1H-NMR has been used to monitor Ca(2+)-induced changes in the mutant proteins, and the spectral changes observed for each mutant have been compared to those for wild-type CaM. In this way, the effect of each mutation on both the mutated site and the other Ca(2+)-binding sites has been examined. The mutation of glutamate to glutamine at position 12 in any of the EF-hand Ca(2+)-binding loops greatly decreases the Ca(2+)-binding affinity at that site, yet differs in the overall effects on Ca2+ binding depending on which of the four sites is mutated. When the mutation is in site I, there is only a small decrease in the apparent Ca(2+)-binding affinity of site II, and vice versa. Mutation in either site III or IV results in a large decrease in the apparent Ca(2+)-binding affinities of the partner C-terminal site. In both the N- and C-terminal domains, evidence for altered conformational effects in the partners of mutated sites is presented. In the C-terminus, the conformational consequences of mutating site III or site IV are strikingly different.

PubMed Disclaimer

Similar articles

Cited by

References

    1. J Biochem. 1984 Oct;96(4):1175-82 - PubMed
    1. Biochim Biophys Acta. 1984 Dec 7;791(2):164-72 - PubMed
    1. Biochemistry. 1983 May 10;22(10):2309-13 - PubMed
    1. J Biochem. 1981 Nov;90(5):1493-505 - PubMed
    1. Biochemistry. 1980 Jan 8;19(1):207-15 - PubMed

Publication types

MeSH terms

Substances

LinkOut - more resources