Identification of a functional switch for actin severing by cytoskeletal proteins.
Actin severing is vital for the organization of the actin cytoskeleton during cell motility. Severing of F-actin by the homologous proteins villin and gelsolin requires unphysiologically high calcium concentrations (20-200 microM). Here we demonstrate that high calcium releases an autoinhibited conformation in villin that is maintained by two low affinity calcium binding sites (aspartic acids 467 and 715) that interact with a cluster of basic residues in the S2 domain of villin. Mutation of either of these sites as well as tyrosine phosphorylation alters the conformation of villin resulting in a protein that can sever actin in nanomolar calcium. These results suggest that tyrosine phosphorylation rather than high calcium may be the mechanism by which villin and other related proteins sever actin in vivo.
Kumar
Narendra
N
Department of Physiology, University of Tennessee Health Science Center, Memphis, Tennessee 38163, USA.
Khurana
Seema
S
D000199:Actins / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002118:Calcium / Q000494:pharmacology*; D002352:Carrier Proteins / Q000737:chemistry / Q000502:physiology*; D018260:Gelsolin / Q000502:physiology; D006801:Humans; D008840:Microfilament Proteins / Q000737:chemistry / Q000502:physiology*; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011487:Protein Conformation
D000199:Actins; D002352:Carrier Proteins; D018260:Gelsolin; D008840:Microfilament Proteins; C026615:villin; D002118:Calcium