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GTP drives myosin light chain 1 interaction with the class V myosin Myo2 IQ motifs via a Sec2 RabGEF‐mediated pathway
Author(s) -
Bielli Pamela,
Casavola Elena Caroli,
Biroccio Antonino,
Urbani Andrea,
RagniniWilson Antonella
Publication year - 2006
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2006.05041.x
Subject(s) - rab , calmodulin , biology , cytokinesis , gtpase , gtp' , microbiology and biotechnology , myosin , myosin light chain kinase , gtp binding protein regulators , guanine nucleotide exchange factor , biochemistry , g protein , signal transduction , cell division , cell , enzyme
Summary The yeast myosin light chain 1 (Mlc1p) belongs to a branch of the calmodulin superfamily and is essential for vesicle delivery at the mother‐bud neck during cytokinesis due to is ability to bind to the IQ motifs of the class V myosin Myo2p. While calcium binding to calmodulin promotes binding/release from the MyoV IQ motifs, Mlc1p is unable to bind calcium and the mechanism of its interaction with target motifs has not been clarified. The presence of Mlc1p in a complex with the Rab/Ypt Sec4p and with Myo2p suggests a role for Mlc1p in regulating Myo2p cargo binding/release by responding to the activation of Rab/Ypt proteins. Here we show that GTP or GTPγS potently stimulate Mlc1p interaction with Myo2p IQ motifs. The C‐terminus of the Rab/Ypt GEF Sec2p, but not Sec4p activation, is essential for this interaction. Interestingly, overexpression of constitutively activated Ypt32p, a Rab/Ypt protein that acts upstream of Sec4p, stimulates Mlc1p/Myo2p interaction similarly to GTP although a block of Ypt32 GTP binding does not completely abolish the GTP‐mediated Mlc1p/Myo2p interaction. We propose that Mlc1p/Myo2p interaction is stimulated by a signal that requires Sec2p and activation of Ypt32p.