An isoform of the phosphatidylinositol-transfer protein transfers sphingomyelin and is associated with the Golgi system.
An isoform of the phosphatidylinositol-transfer protein (PI-TP) was identified in the cytosol fraction of bovine brain. This protein, designated PI-TP beta, has an apparent molecular mass of 36 kDa and an isoelectric point of 5.4. The N-terminal amino acid sequence (21 residues) is 90% similar to that of bovine brain PI-TP, henceforth designated PI-TP alpha (molecular mass 35 kDa and pI 5.5). As observed for PI-TP alpha, PI-TP beta has a distinct preference for phosphatidylinositol over phosphatidylcholine. In addition, it expresses a high transfer activity towards sphingomyelin. PI-TP alpha lacks this activity completely. By indirect immunofluorescence we demonstrated that, in Swiss mouse 3T3 fibroblasts, PI-TP beta is preferentially associated with the Golgi system whereas PI-TP alpha is predominantly present in the cytoplasm and the nucleus. In cytosol-depleted HL60 cells, both PI-TP alpha and PI-TP beta were equally effective at reconstituting guanosine 5'-[gamma-thio]triphosphate-mediated phospholipase C beta activity.
de Vries
K J
KJ
Centre for Biomembranes and Lipid Enzymology, Utrecht University, The Netherlands.
Heinrichs
A A
AA
Cunningham
E
E
Brunink
F
F
Westerman
J
J
Somerharju
P J
PJ
Cockcroft
S
S
Wirtz
K W
KW
Snoek
G T
GT
D016475:3T3 Cells; D000595:Amino Acid Sequence; D000818:Animals; D001921:Brain / Q000378:metabolism*; D002352:Carrier Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D002417:Cattle; D002460:Cell Line; D002846:Chromatography, Affinity; D002848:Chromatography, DEAE-Cellulose; D002850:Chromatography, Gel; D003600:Cytosol / Q000378:metabolism; D006056:Golgi Apparatus / Q000378:metabolism*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D006801:Humans; D015473:Leukemia, Promyelocytic, Acute; D008565:Membrane Proteins; D051379:Mice; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010713:Phosphatidylcholines / Q000378:metabolism; D049294:Phospholipid Transfer Proteins; D051381:Rats; D029701:Saccharomyces cerevisiae Proteins; D017386:Sequence Homology, Amino Acid; D013109:Sphingomyelins / Q000378:metabolism*; D013379:Substrate Specificity; D014407:Tumor Cells, Cultured; D010738:Type C Phospholipases / Q000378:metabolism
D002352:Carrier Proteins; D008565:Membrane Proteins; D010713:Phosphatidylcholines; D049294:Phospholipid Transfer Proteins; C118289:SEC24 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D013109:Sphingomyelins; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D010738:Type C Phospholipases