The photoaffinity probe 8-N3[alpha-32P]ATP labels the ATP-binding sites of rabbit neutrophil and skeletal muscle actin.

8-Azido-[alpha-32P]ATP (8-N3-ATP) was used as a photoaffinity label for ATP binding sites in the subcellular fractions of rabbit peritoneal neutrophils. The radioactive 8-N3-ATP was specifically incorporated into one major protein of 43 kDa. The isoelectric point, molecular mass and subcellular distribution of this labeled protein closely resemble those of the actin. 8-N3-[alpha-32P]ATP was further tested as a photoaffinity label for the ATP binding site in the purified rabbit skeletal muscle G-actin. The radioactive 8-N3-ATP was specifically incorporated into the actin band in SDS-polyacrylamide gel. The results indicate that 8-N3-ATP can be used as a photoaffinity label for actin.