Location of sites in human lipocortin I that are phosphorylated by protein tyrosine kinases and protein kinases A and C.
Lipocortin I is a 39-kilodalton membrane-associated protein that in A431 cells is phosphorylated on tyrosine in response to epidermal growth factor (EGF). We have used recombinant human lipocortin I as a substrate for several protein kinases and identified phosphorylated residues by a combination of peptide mapping and sequence analysis. Lipocortin I was phosphorylated near the amino terminus at Tyr-21 by recombinant pp60c-src. The same tyrosine residue was phosphorylated by polyoma middle T/pp60c-src complex, by recombinant pp50v-abl, and with A431 cell membranes by the EGF receptor/kinase. The primary site of phosphorylation by protein kinase C was also near the amino terminus at Ser-27. The major site of phosphorylation by adenosine cyclic 3',5'-phosphate dependent protein kinase was on the carboxy-terminal half of the molecule at Thr-216. These sites are compared to the phosphorylation sites previously located in the structurally related protein lipocortin II.
Varticovski
L
L
Department of Physiology, Tufts University School of Medicine, Boston, Massachusetts 02111.
Chahwala
S B
SB
Whitman
M
M
Cantley
L
L
Schindler
D
D
Chow
E P
EP
Sinclair
L K
LK
Pepinsky
R B
RB
D000595:Amino Acid Sequence; D017302:Annexins; D002460:Cell Line; D005341:Fibrinolysin; D006023:Glycoproteins / Q000378:metabolism*; D006801:Humans; D010446:Peptide Fragments / Q000032:analysis; D010449:Peptide Mapping; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism*; D011494:Protein Kinases / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D016392:Proto-Oncogene Proteins pp60(c-src); D011994:Recombinant Proteins / Q000378:metabolism*; D014357:Trypsin
D017302:Annexins; D006023:Glycoproteins; D010446:Peptide Fragments; D011518:Proto-Oncogene Proteins; D011994:Recombinant Proteins; D011494:Protein Kinases; D011505:Protein-Tyrosine Kinases; D016392:Proto-Oncogene Proteins pp60(c-src); D011493:Protein Kinase C; D014357:Trypsin; D005341:Fibrinolysin