Actin binding and proline rich motifs of CR16 play redundant role in growth of vrp1Δ cells

CR16, (Glucocorticoid-regulated) belongs to the verprolin family of proteins which are characterized by the presence of a V domain (verprolin) at the N-terminal. Expression of CR16 suppressed the growth and endocytosis defect of vrp1Δ strain without correcting the actin patch polarization defect. The V domain of CR16 is critical for suppression of the growth defect of vrp1Δ strain but not for localisation to cortical actin patches. Mutations in the actin binding motif alone did not abolish the activity of CR16 but the mutations in combination with deletion of N-terminal proline rich motif abolished the ability of CR16 to suppress the growth defect. This suggests that the V domain of CR16 has two functionally redundant motifs and either one of these motifs is sufficient for suppressing the growth defect of vrp1Δ strain. This is in contrast to the observation that both WIP and WIRE require the actin binding motif for their activity.