Platelet cytosolic 44-kDa protein is a substrate of cholera toxin-induced ADP-ribosylation and is not recognized by antisera against the. alpha. subunit of the stimulatory guanine nucleotide-binding regulatory protein

Journal Article · Mon Aug 01 00:00:00 EDT 1988 · Proceedings of the National Academy of Sciences of the United States of America; (USA)

DOI:https://doi.org/10.1073/pnas.85.16.5899· OSTI ID:5641944

Molina Y Vedia, L M; Reep, B R; Lapetina, E G ^[1]

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1. Burroughs Wellcome Co., Research Triangle Park, NC (USA)

ADP-ribosylation induced by cholera toxin and pertussis toxin was studied in particulate and cytosolic fractions of human platelets. Platelets were disrupted by a cycle of freezing and thawing in the presence of a hyposmotic buffer containing protease inhibitors. In both fractions, the A subunit of cholera toxin ADP-ribosylates two proteins with molecular masses of 42 and 44 kDa, whereas pertussis toxin ADP-ribosylates a 41-kDa polypeptide. Two antisera against the {alpha} subunit of the stimulatory guanine nucleotide-binding regulatory protein recognize only the 42-kDa polypeptide. Cholera toxin-induced ADP-ribosylation of the 42- and 44-kDa proteins is reduced by pretreatment of platelets with iloprost, a prostacyclin analog. The 44-kDa protein, which is substrate of cholera toxin, could be extracted completely from the membrane and recovered in the cytosolic fraction when the cells were disrupted by Dounce homogenization and the pellet was extensively washed. A 44-kDa protein can also be labeled with 8-azidoguanosine 5{prime}-({alpha}-{sup 32}P)triphosphate in the cytosol and membranes. These finding indicate that cholera and pertussis toxins produced covalent modifications of proteins present in particulate and cytosolic platelet fractions. Moreover, the 44-kDa protein might be an {alpha} subunit of a guanine nucleotide-binding regulatory protein that is not recognized by available antisera.

• OSTI ID: 5641944
• Journal Information: Proceedings of the National Academy of Sciences of the United States of America; (USA), Vol. 85:16; ISSN 0027-8424
• Country of Publication: United States
• Language: English

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59 BASIC BIOLOGICAL SCIENCES
BLOOD PLATELETS
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PROTEINS
MOLECULAR STRUCTURE
TOXINS
SUBSTRATES
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AUTORADIOGRAPHY
ELECTROPHORESIS
GUANINE
IMMUNE SERUMS
IODINE 125
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BLOOD CELLS
BODY FLUIDS
CARBOHYDRATES
CHEMISTRY
DAYS LIVING RADIOISOTOPES
ELECTRON CAPTURE RADIOISOTOPES
HETEROCYCLIC COMPOUNDS
HYDROXY COMPOUNDS
INTERMEDIATE MASS NUCLEI
IODINE ISOTOPES
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NUCLEI
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550201* - Biochemistry- Tracer Techniques