END4P SLA2P INTERACTS WITH ACTIN-ASSOCIATED PROTEINS FOR ENDOCYTOSIS IN SACCHAROMYCES-CEREVISIAE/

end4-1 was isolated as a temperature-sensitive endocytosis mutant. We cloned and sequenced END4 and found that it is identical to SLA2/MOP2. This gene is required for growth at high temperature, viability in th e absence of Abp1p, polarization of the cortical actin cytoskeleton, a nd endocytosis. We used a mutational analysis of END4 to correlate in vivo functions with regions of End4p and we found that two regions of End4p participate in endocytosis but that the talin-like domain of End 4p is dispensable. The N-terminal domain of End4p is required for grow th at high temperature, endocytosis, and actin organization. A central coiled-coil domain of End4p is necessary for formation of a soluble s edimentable complex. Furthermore, this domain has an endocytic functio n that is redundant with the function(s) of ABP1 and SRV2. The endocyt ic function of Abp1p depends on its SH3 domain. In addition we have is olated a recessive negative allele of SRV2 that is defective for endoc ytosis. Combined biochemical, functional, and genetic analysis lead us to propose that End4p may mediate endocytosis through interaction wit h other actin-associated proteins, perhaps Rvs167p, a protein essentia l for endocytosis.