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 GTPgammaS 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.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Amino Acid Motifs
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GTP-Binding Proteins / genetics
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GTP-Binding Proteins / metabolism*
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Guanine Nucleotide Exchange Factors
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Guanosine 5'-O-(3-Thiotriphosphate) / pharmacology
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Guanosine Triphosphate / metabolism*
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Guanosine Triphosphate / pharmacology
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Myosin Heavy Chains / genetics
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Myosin Heavy Chains / metabolism*
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Myosin Light Chains / genetics
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Myosin Light Chains / metabolism*
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Myosin Type V / genetics
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Myosin Type V / metabolism*
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Saccharomyces cerevisiae / drug effects
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Saccharomyces cerevisiae / metabolism
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Saccharomyces cerevisiae Proteins / drug effects
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Saccharomyces cerevisiae Proteins / genetics
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Saccharomyces cerevisiae Proteins / metabolism*
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Signal Transduction*
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rab GTP-Binding Proteins / genetics
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rab GTP-Binding Proteins / metabolism*
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rab1 GTP-Binding Proteins / genetics
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rab1 GTP-Binding Proteins / metabolism*
Substances
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Guanine Nucleotide Exchange Factors
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MLC1 protein, S cerevisiae
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MYO2 protein, S cerevisiae
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Myosin Light Chains
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SEC2 protein, S cerevisiae
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Saccharomyces cerevisiae Proteins
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Guanosine 5'-O-(3-Thiotriphosphate)
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Guanosine Triphosphate
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YPT31 protein, S cerevisiae
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GTP-Binding Proteins
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Myosin Type V
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YPT32 protein, S cerevisiae
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SEC4 protein, S cerevisiae
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Myosin Heavy Chains
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rab GTP-Binding Proteins
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rab1 GTP-Binding Proteins