Effect of mutations imitating the phosphorylation by TRPM7 kinase on the function of the N-terminal domain of tropomodulin

It has been shown that tropomodulin 1 is phosphorylated at serine and threonine residues by TRPM7 kinase. The phosphorylation sites for TRPM7 in the N-terminal functional domain of tropomodulin 1 have been identified, which include tropomyosin-binding and actin-capping regions. It has been found that the phosphorylation-mimicking mutation T54E resulted in the loss of capping ability of the N-terminal tropomodulin domain; however, its tropomyosin-binding ability did not change. We further hypothesize that the phosphorylation of tropomodulin by TRPM7 kinase may play a role in the regulation of the dynamics of actin filaments.