Mlc1p an essential light chain (ELC) for Myo1p, binding to its IQ1 motif, while Mlc2p is a regulatory light chain (RLC) for Myo1p (3, 4). Mlc1p is also a light chain for the type V myosin Myo2p (1) and the IQGAP-like protein, Iqg1p (5).

MLC1 is an essential gene and exhibits haploinsufficiency (1). Mlc1p localizes to the bud neck and its interactions with Myo1p and Iqg1p play a role in actin ring formation and promote targeted membrane deposition at the bud neck (3) during cytokinesis. Inviable mlc1 null mutant cells show a defect in cytokinesis, resulting in enlarged, multinucleate cells (1), a phenotype similar to cells deleted for IQG1 (6). Disruption of the Mlc1p-Myo1p or Mlc1p-Myo2p interaction does not prevent Mlc1p targeting to the bud neck. However, disrupting the Mlc1p-Iqg1p interaction by depleting Mlc1p prevents localization of Iqg1p to the bud neck which in turn prevents actin localization to the bud neck and actomyosin ring formation (4, 5). Thus, the Mlc1p-Iqg1p interaction plays a major role in cytokinesis. Mlc1p associates with secretory vesicles and forms a complex(es) with Sec4p and Myo2p and is required for vesicle targeting during cytokinesis (2).

Compared to the RLCs, the sequence of the ELCs are better conserved. Mlc1p is similar to S. pombe ELC (CDC4), D. discoideum ELC, chicken light chain (MLE1 gene) and Acanthamoeba myosin light chain (3 and references therein).

Last updated: 2007-02-15