5dsu
Crystal structure of double mutant of N-domain of human calmodulin
Structural highlights
DiseaseCALM1_HUMAN The disease is caused by mutations affecting the gene represented in this entry. Mutations in CALM1 are the cause of CPVT4. The disease is caused by mutations affecting the gene represented in this entry. Mutations in CALM1 are the cause of LQT14. FunctionCALM1_HUMAN Calmodulin mediates the control of a large number of enzymes, ion channels, aquaporins and other proteins through calcium-binding. Among the enzymes to be stimulated by the calmodulin-calcium complex are a number of protein kinases and phosphatases. Together with CCP110 and centrin, is involved in a genetic pathway that regulates the centrosome cycle and progression through cytokinesis (PubMed:16760425). Mediates calcium-dependent inactivation of CACNA1C (PubMed:26969752). Positively regulates calcium-activated potassium channel activity of KCNN2 (PubMed:27165696).[1] [2] [3] [4] Publication Abstract from PubMedDouble mutation of Q41L and K75I in the N-domain of calmodulin (N-Cam) stabilizes the closed form of N-Cam such that binding of Ca2+ in solution no longer triggers a conformational change to the open form, and its Ca2+ binding affinity decreases dramatically. To further investigate the solvation effects on the structure, Ca2+ binding affinity and conformational dynamics of this N-Cam double mutant in the Ca2+ saturated state, we solved its X-ray structure. Surprisingly, the structure revealed an open conformation of the domain which contradicts its closed conformation in solution. Here we provide evidence that crystallization conditions were responsible for this Ca2+-saturated domain open conformation in the crystal. Importantly, we demonstrate that the presence of the crystallization co-precipitant and alcohols were able to induce a progressive opening of the closed form of this domain, in Ca2+ saturated state, in solution. However, in the Ca2+ depleted state, addition of alcohols was unable to induce any opening of this domain in solution. In addition, in the Ca2+ saturated state, the molecular dynamics simulations show that while N-Cam can populate the open and closed conformation, the N-Cam double mutant exclusively populates the closed conformation. Our results provide experimental evidence of intermediate conformations of Ca2+-saturated N-Cam in solution. We propose that conformational change of Ca2+ sensor EF-hand domains depends on solvation energetics, Ca2+ binding to promote the full open form, Ca2+ depleted state conformational dynamics, and the chemical properties of the molecules nearby key residues such as those at positions 41 and 75 in N-Cam. On the Ca2+ binding and conformational change in EF-hand domains: Experimental evidence of Ca2+-saturated intermediates of N-domain of calmodulin.,Ababou A, Zaleska M, Pfuhl M Biochim Biophys Acta. 2017 Mar 10;1865(6):640-651. doi:, 10.1016/j.bbapap.2017.03.003. PMID:28288938[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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