Mutant rat phosphatidylinositol/phosphatidylcholine transfer proteins specifically defective in phosphatidylinositol transfer: implications for the regulation of phospholipid transfer activity.
The mammalian phosphatidylinositol/phosphatidylcholine transfer proteins (PI-TPs) catalyze exchange of phosphatidylinositol (PI) or phosphatidylcholine (PC) between membrane bilayers in vitro. We find that Ser-25, Thr-59, Pro-78, and Glu-248 make up a set of rat (r) PI-TP residues, substitution of which effected a dramatic reduction in the relative specific activity for PI transfer activity without significant effect on PC transfer activity. Thr-59 was of particular interest as it is a conserved residue in a highly conserved consensus protein kinase C phosphorylation motif in metazoan PI-TPs. Replacement of Thr-59 with Ser, Gln, Val, Ile, Asn, Asp, or Glu effectively abolished PI transfer capability but was essentially silent with respect to PC transfer activity. These findings identify rPI-TP residues that likely cooperate to form a PI head-group binding/recognition site or that lie adjacent to such a site. Finally, the selective sensitivity of the PI transfer activity of rPI-TP to alteration of Thr-59 suggests a mechanism for in vivo regulation of rPI-TP activity.
Alb
J G
JG
Department of Cell Biology, University of Alabama at Birmingham 35294-0005, USA.
Gedvilaite
A
A
Cartee
R T
RT
Skinner
H B
HB
Bankaitis
V A
VA
D000727:Androgen-Binding Protein; D000818:Animals; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins; D008954:Models, Biological; D008969:Molecular Sequence Data; D009154:Mutation; D010713:Phosphatidylcholines / Q000378:metabolism*; D010716:Phosphatidylinositols / Q000378:metabolism*; D049294:Phospholipid Transfer Proteins; D010743:Phospholipids / Q000378:metabolism*; D060789:Prostatein; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins; D060765:Secretoglobins; D013329:Structure-Activity Relationship; D014598:Uteroglobin; D060788:Mammaglobin B
D000727:Androgen-Binding Protein; D002352:Carrier Proteins; D008565:Membrane Proteins; D010713:Phosphatidylcholines; D010716:Phosphatidylinositols; D049294:Phospholipid Transfer Proteins; D010743:Phospholipids; D060789:Prostatein; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; D060765:Secretoglobins; D014598:Uteroglobin; C118289:SEC24 protein, S cerevisiae; C511484:Scgb1d2 protein, rat; C511483:Scgb1d4 protein, rat; C556468:Scgb2a1 protein, rat; D060788:Mammaglobin B