The yeast VAP homolog Scs2p has a phosphoinositide-binding ability that is correlated with its activity.
The yeast VAMP-associated protein (VAP) homolog Scs2p is an endoplasmic reticulum (ER)/nuclear membrane protein that binds to an FFAT (diphenylalanine in an acidic tract) motif found in various lipid-metabolic proteins, including Opi1p, a negative regulator of phospholipid biosynthesis. Here, we show that Scs2p is a novel phosphoinositide-binding protein that can bind to phosphatidylinositol monophosphates and bisphosphates in vitro. The phosphoinositide-binding domain was assigned to the N-terminal major sperm protein (MSP) domain which also contains the FFAT-binding domain. When several lysine residues in the MSP domain were substituted for alanine, the resulting mutant Scs2 proteins lost the phosphoinositide-binding ability and failed to complement the inositol auxotrophy of an scs2 deletion strain. However, the mutant proteins still localized in the ER/nuclear membrane, in a similar manner to wild-type Scs2p. These results suggest the possibility that Scs2p activity is regulated by phosphoinositides to coordinate phospholipid biosynthesis in response to changes in phospholipid composition.
Kagiwada
Satoshi
S
Department of Biological Sciences, Faculty of Science, Nara Women's University, Nara 630-8506, Japan. kagiwada@cc.nara-wu.ac.jp
Hashimoto
Misa
M
D001665:Binding Sites; D002462:Cell Membrane / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism*; D010716:Phosphatidylinositols / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D013223:Statistics as Topic
D008565:Membrane Proteins; D010716:Phosphatidylinositols; D029701:Saccharomyces cerevisiae Proteins; C501314:Scs2 protein, S cerevisiae