Mob2Cbk1

Mob2Cbk1 refers to the functional kinase complex formed by Mob2 and Cbk1 in fungi, primarily Saccharomyces cerevisiae. The complex is a core component of the RAM (Regulation of Ace2 and Morphogenesis) pathway, which orchestrates cell polarity, morphogenesis, and daughter cell separation during budding.

Cbk1 is an NDR family serine/threonine kinase; Mob2 is a regulatory cofactor/partner that binds to the C-terminal regulatory region of Cbk1 and stimulates its activity. The Mob2–Cbk1 complex localizes to sites of polarized growth, such as the budding site and the daughter cell–mother cell neck, and becomes activated during late mitosis and cytokinesis.

One of the key outputs of Mob2Cbk1 signaling is the regulation of Ace2, a transcription factor that promotes expression of genes required for cell separation, including CTS1. Phosphorylation of Ace2 by Cbk1 promotes its retention in the nucleus of daughter cells, driving the asymmetric gene expression that underpins proper cytokinesis. The RAM pathway also influences polarized growth and maintenance of cell polarity through additional effectors and transcriptional programs.

Conservation and variation: The Mob2–Cbk1 interaction is conserved across fungi, with orthologous relationships to other Mob–NDR kinase pairs. In pathogenic species such as Candida albicans, RAM pathway components contribute to morphogenesis and virulence, highlighting potential antifungal targets. In literature, Mob2Cbk1 is discussed as a functional unit rather than a single polypeptide, reflecting its role as a signaling module.