Calcium binding decreases the stokes radius of calmodulin and mutants R74A, R90A, and R90G

B R Sorensen; M A Shea

doi:10.1016/S0006-3495(96)79535-8

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Calcium binding decreases the stokes radius of calmodulin and mutants R74A, R90A, and R90G

Journal article

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Peer reviewed

Calcium binding decreases the stokes radius of calmodulin and mutants R74A, R90A, and R90G

B R Sorensen and M A Shea

Biophysical journal, Vol.71(6), pp.3407-3420

12/1996

DOI: 10.1016/S0006-3495(96)79535-8

PMCID: PMC1233828

PMID: 8968610

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https://doi.org/10.1016/S0006-3495(96)79535-8View

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Abstract

Calmodulin (CaM) is an intracellular cooperative calcium-binding protein essential for activating many diverse target proteins. Biophysical studies of the calcium-induced conformational changes of CaM disagree on the structure of the linker between domains and possible orientations of the domains. Molecular dynamics studies have predicted that Ca4(2+)CaM is in equilibrium between an extended and compact conformation and that Arg74 and Arg90 are critical to the compaction process. In this study gel permeation chromatography was used to resolve calcium-induced changes in the hydrated shape of CaM at pH 7.4 and 5.6. Results showed that mutation of Arg 74 to Ala increases the R(s) as predicted; however, the average separation of domains in Ca4(2+)-CaM was larger than predicted by molecular dynamics. Mutation of Arg90 to Ala or Gly affected the dimensions of apo-CaM more than those of Ca4(2+)-CaM. Calcium binding to CaM and mutants (R74A-CaM, R90A-CaM, and R90G-CaM) lowered the Stokes radius (R(s)). Differences between R(s) values reported here and Rg values determined by small-angle x-ray scattering studies illustrate the importance of using multiple techniques to explore the solution properties of a flexible protein such as CaM.

Recombinant Proteins - metabolism

Amino Acid Sequence

Models, Structural

Calmodulin - metabolism

Mutagenesis, Site-Directed

Protein Structure, Secondary

Calcium - metabolism

Molecular Sequence Data

Rats

Recombinant Proteins - chemistry

DNA Primers

Point Mutation

Animals

Base Sequence

Protein Binding

Protein Conformation

Calmodulin - chemistry

Binding Sites

Hydrogen-Ion Concentration

Details

Title: Subtitle: Calcium binding decreases the stokes radius of calmodulin and mutants R74A, R90A, and R90G
Creators: B R Sorensen - Department of Biochemistry, University of Iowa College of Medicine, Iowa City 52242-1109, USA
M A Shea
Resource Type: Journal article
Publication Details: Biophysical journal, Vol.71(6), pp.3407-3420
Publisher: United States
DOI: 10.1016/S0006-3495(96)79535-8
PMID: 8968610
PMCID: PMC1233828
ISSN: 0006-3495
eISSN: 1542-0086
Grant note: DK 25295 / NIDDK NIH HHS
Language: English
Date published: 12/1996
Academic Unit: Molecular Physiology and Biophysics; Iowa Neuroscience Institute; Biochemistry and Molecular Biology
Record Identifier: 9984024519602771

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