GTP drives myosin light chain 1 interaction with the class V myosin Myo2 IQ motifs via a Sec2 RabGEF-mediated pathway

Pamela Bielli, Elena Caroli Casavola, Antonino Biroccio, Andrea Urbani, Antonella Ragnini-Wilson

Research output: Contribution to journalArticle

Abstract

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.

Original languageEnglish
Pages (from-to)1576-1590
Number of pages15
JournalMolecular Microbiology
Volume59
Issue number5
DOIs
Publication statusPublished - Mar 2006

ASJC Scopus subject areas

  • Molecular Biology
  • Microbiology

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