<p>(<b>A</b>) Msb1 interacts with Boi2 and Boi1 by GST pull-down assay. Cells of yeast strain YEF1395 (<i>msb1</i>Δ) carrying YEp181-3HA-MSB1 along with pEGKT (GST), pEGKT-CDC42 (Cdc42), pEGKT-BEM1 (Bem1), pEGKT-CDC24 (Cdc24), pEGKT-BOI1 (Boi1), or pEGKT-BOI2 (Boi2), as well as cells of yeast strain JGY2425 (<i>boi1</i>Δ) or JGY2349 (<i>boi2</i>Δ) carrying YEp181-3HA-MSB1/pEGKT or YEp181-3HA-MSB1/pEGKT-BOI1 were used in the assay. (<b>B</b>) Msb1 interacts with the C-terminal region of Boi1 and Boi2 lacking the proline-rich motif. Left panel, the schematic diagram of domain structure in Boi1 and Boi2. P, proline-rich motif. Right panel, GST pull-down assay with GST-tagged Boi2, Boi2-C, and Boi1-C in yeast strains YEF473A (WT), JGY2425 (<i>boi1</i>Δ), and JGY2349 (<i>boi2</i>Δ). (<b>C</b>) Msb1 interacts with Cdc42 in <i>boi1</i>Δ <i>boi2</i>Δ cells. GST pull-down assay was performed in cells of yeast strain YEF473A (WT) and JGY2821 (<i>boi1</i>Δ <i>boi2</i>Δ) carrying YEp181-3HA-MSB1/pEGKT or YEp181-3HA-MSB1/pEGKT-CDC42. Molecular weight of GST-tagged proteins: Cdc42 (46 kDa), Bem1 (86 kDa), Cdc24 (120 kDa), Boi1 (133 kDa), Boi2 (140 kDa), Boi1-C (88 kDa), and Boi2-C (90 kDa).</p
