Evidence that apoB-100 of low-density lipoproteins is a novel Src-related protein kinase.
Protein-tyrosine kinases of signal transduction pathways occur and function intracellularly. In contrast, the low-density lipoprotein (LDL) particle circulates in plasma, where its function is to solubilize and transport lipid. Recently, several reports showed that LDL may have a role in signal transduction. We have identified a region in the apoB-100 primary structure which shows similarity to Src-homology-1 (SH1) domains, the kinase region of protein-tyrosine kinases. Results obtained in protein kinase assays of highly purified LDL showed that only the apoB-100 was phosphorylated, suggesting that apoB-100 has the capacity to undergo autophosphorylation like known protein-tyrosine kinases. Phosphorylation was not observed for any other apolipoprotein in LDL or for any component of high-density lipoprotein and lipoprotein [a]. Our results suggest that apoB-100 may be a novel and functional member of the src protein kinase family.
Guevara
J
J
Department of Medicine, Baylor College of Medicine, Houston, Texas 77030, USA.
Walch
E T
ET
Epstein
H F
HF
Sparrow
J T
JT
Gotto
A M
AM
Valentinova
N V
NV
D000595:Amino Acid Sequence; D053299:Apolipoprotein B-100; D001055:Apolipoproteins B / Q000737:chemistry* / Q000378:metabolism; D008077:Lipoproteins, LDL / Q000378:metabolism*; D008969:Molecular Sequence Data; D010766:Phosphorylation; D017385:Sequence Homology; D015398:Signal Transduction; D018909:src Homology Domains; D019061:src-Family Kinases / Q000737:chemistry* / Q000378:metabolism
D053299:Apolipoprotein B-100; D001055:Apolipoproteins B; D008077:Lipoproteins, LDL; D019061:src-Family Kinases