Crystallization, X-ray characterization and selenomethionine phasing of Mlc1p bound to IQ motifs from myosin V.

Mlc1p is a calmodulin-like protein from the budding yeast Saccharomyces cerevisiae, where it has been identified as a subunit of a class V myosin, Myo2p, and a binding partner of an IQGAP-like protein, Iqg1p. Through its interactions with these two proteins, Mlc1p plays a role in polarized growth and cytokinesis. Mlc1p has been crystallized in complexes with four different IQ target motifs from the neck region of Myo2p: IQ2, IQ3, IQ4 and IQ2-IQ3 (referred to as IQ2,3). Electron-density maps for two of the complexes (Mlc1p-IQ4 and Mlc1p-IQ2,3) were obtained from multiple anomalous dispersion (MAD) experiments based on selenomethionine derivatives. The other two structures (Mlc1p-IQ2 and Mlc1p-IQ3) were determined by molecular replacement using the partially refined structure of Mlc1p-IQ2,3 as a search model.