title: The photoaffinity probe 8-azidoadenosine 5'-triphosphate selectively labels the heavy chain of Chlamydomonas 12 S dynein.
abstract: Chlamydomonas 12 S dynein, which makes up part of the outer arm of the flagellar axoneme, consists of three polypeptides of 330,000, 22,000, and 18,000 daltons. We have used 8-azidoadenosine 5'-triphosphate (8-N3ATP), a photoaffinity analog of ATP, to investigate which of the dynein polypeptides contains the site of ATP hydrolysis. 8-N3ATP is a competitive inhibitor of the hydrolysis of ATP by 12 S dynein and is hydrolyzed by 12 S dynein in an ATP- and vanadate-sensitive fashion, indicating that it binds to the 12 S dynein hydrolytic site in the same way as ATP. When dynein was incubated with [gamma-32P]- or [alpha-32P]8-N3ATP in the presence of UV light to activate the azido moiety, the analog was incorporated into 12 S dynein's heavy polypeptide chain, but not its light chains. The incorporation was UV-dependent, was blocked by addition of ATP or vanadate plus ADP to the reaction mixture, and did not occur in heat-denatured dynein. These results strongly suggest that the hydrolytic site of 12 S dynein is contained in its heavy chain.
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives* / Q000378:metabolism; D000345:Affinity Labels / Q000378:metabolism*; D001386:Azides / Q000378:metabolism*; D001667:Binding, Competitive; D002696:Chlamydomonas / Q000201:enzymology*; D004398:Dyneins / Q000378:metabolism*; D005407:Flagella / Q000201:enzymology; D007700:Kinetics; D046911:Macromolecular Substances; D011485:Protein Binding
chemical_list: D000345:Affinity Labels; D001386:Azides; D046911:Macromolecular Substances; C017040:8-azidoadenosine 5'-triphosphate; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; D004398:Dyneins