Mk. Balasubramanian et al., FISSION YEAST SOP2P - A NOVEL AND EVOLUTIONARILY CONSERVED PROTEIN THAT INTERACTS WITH ARP3P AND MODULATES PROFILIN FUNCTION, EMBO journal, 15(23), 1996, pp. 6426-6437
Profilins bind to monomeric actin and also interact with ligands such
as phosphoinositide 4,5-bisphosphate, the proline-rich protein VASP an
d a complex of four to six polypeptides identified in Acanthamoeba tha
t includes two actin-related proteins, Here, we report the identificat
ion and characterization of an essential gene from Schizosaccharomyces
pombe, sop2(+), a mutation in which rescues the temperature-sensitive
lethality of a profilin mutation, cdc3-124, The sop2-1 mutant is defe
ctive for cell elongation and septation, suggesting that it is involve
d in multiple cortical actin-requiring processes, Consistent with a ro
le in actin cytoskeletal function, negative interactions have been ide
ntified between sop2-1 and act1-48, a mutant allele of actin, Sop2p is
a novel 377 amino acid polypeptide with similarity to proteins of the
beta-transducin repeat family. Sop2p-related proteins have been ident
ified by sequencing projects in diverse species, and we have isolated
a human cDNA highly related to sop2(+), SOP2 Hs, which functionally co
mplements the sop2-1 mutation, Sop2p proteins from all species contain
peptide sequences identical or highly similar to two peptide sequence
s from an Acanthamoeba beta-transducin repeat protein present in the p
rofilin binding complex, Biochemical analyses demonstrate that Sop2p i
s present in a complex which also contains the actin-related protein,
Arp3p, Immunofluorescence studies reveal the presence of Sop2p in (i)
punctate structures distributed throughout the cell, (ii) cables that
extend the length of the cell, and (iii) a medial band in a small perc
entage of septating cells, Collectively these data demonstrate the int
eraction of Sop2p with Arp3p, profilin and actin.