Can calmodulin function without binding calcium?

• Published in: Cell Vol. 65; no. 6; pp. 949 - 959
• Main Authors: Geiser, John R., van Tuinen, Diederik, Brockerhoff, Susan E., Neff, Michael M., Davis, Trisha N.
• Format: Journal Article
• Language: English
• Published: Cambridge, MA Elsevier Inc 14.06.1991; Cell Press; Elsevier
• Subjects: Amino Acid Sequence; Analytical, structural and metabolic biochemistry; Binding and carrier proteins; Biological and medical sciences; Blotting, Western; calcium; Calcium - metabolism; Calmodulin - immunology; Calmodulin - physiology; DNA Mutational Analysis; Environmental Sciences; Fundamental and applied biological sciences. Psychology; growth; Hot Temperature; Life Sciences; Molecular Sequence Data; mutation; Nitrogen - metabolism; Proteins; Recombinant Proteins - immunology; Recombinant Proteins - metabolism; Saccharomyces cerevisiae; Saccharomyces cerevisiae - physiology; site-directed mutagenesis; Spores, Fungal - physiology; Structure-Activity Relationship; Vegetal Biology; yeasts; Binding protein; Calcium; Structure activity relation; Escherichia coli; Site directed mutagenesis; Microorganism culture; Bacteria; Binding site; Mutation; Calmodulin; Structure composition relationship; Enterobacteriaceae
• ISSN: 0092-8674; 1097-4172
• DOI: 10.1016/0092-8674(91)90547-C

Calmodulin is a small Ca 2+-binding protein proposed to act as the intracellular Ca 2+ receptor that translates Ca 2+ signals into cellular responses. We have constructed mutant yeast calmodulins in which the Ca 2+-binding loops have been altered by site-directed mutagenesis. Each of the mutant proteins has a dramatically reduced affinity for Ca 2+; one does not bind detectable levels of 45Ca 2+ either during gel filtration or when bound to a solid support. Furthermore, none of the mutant proteins change conformation even in the presence of high Ca 2+ concentrations. Surprisingly, yeast strains relying on any of the mutant calmodulins not only survive but grow well. In contrast, yeast strains deleted for the calmodulin gene are not viable. Thus, calmodulin is required for growth, but it can perform its essential function without the apparent ability to bind Ca 2+.