Faculty Collaboration Database

Thrombolamban, the 22-kDa platelet substrate of cyclic AMP-dependent protein kinase, is immunologically homologous with the Ras family of GTP-binding proteins. Proc Natl Acad Sci U S A 1990 Jan;87(2):758-62

Date

01/01/1990

Pubmed ID

1689052

Pubmed Central ID

PMC53345

DOI

10.1073/pnas.87.2.758

Scopus ID

2-s2.0-0025129102 (requires institutional sign-in at Scopus site)   32 Citations

Abstract

Platelet inhibition by agents that increase intracellular levels of cAMP is associated with cAMP-dependent phosphorylation of specific intracellular proteins, including a membrane-associated 22-kDa microsomal protein called thrombolamban. In view of recent studies suggesting that platelets also contain 22-kDa GTP-binding proteins that are homologous with ras-encoded p21 proteins, the present work was undertaken to examine the possibility that thrombolamban and the Ras-like proteins were the same. Platelet microsomes were labeled with [gamma-32P]ATP and the labeled proteins were examined by autoradiography of sodium dodecyl sulfate/polyacrylamide gels. On Western blots of both one-dimensional and two-dimensional gels, thrombolamban immunoreacted with M90, a monoclonal antibody that recognizes the GTP-binding domain of Ras p21 proteins, but not with Y13-259, a monoclonal antibody that recognizes another domain and is specific for Ras proteins. Overlay experiments with unlabeled platelet microsomes demonstrated numerous low molecular weight proteins that bound [alpha-32P]GTP, although none could be identified as thrombolamban. Finally, thrombolamban was immunoprecipitated by M90. These studies show that thrombolamban is a low molecular weight protein that is immunologically related to the Ras family of GTP-binding proteins.

Author List

White TE, Lacal JC, Reep B, Fischer TH, Lapetina EG, White GC 2nd

Author

Gilbert C. White MD Professor in the Medicine department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Adenosine Triphosphate
Antibodies, Monoclonal
Blood Platelets
Blood Proteins
Blotting, Western
Calcium-Binding Proteins
Electrophoresis, Gel, Two-Dimensional
Epitopes
GTP-Binding Proteins
Humans
Isoelectric Focusing
Microsomes
Molecular Weight
Oncogene Protein p21(ras)
Phosphorylation
Protein Kinases