THE REACTION OF GROEL (CPN-60) WITH THE ATP ANALOG 2',3' DIALDEHYDE ATP

The reaction of the E. coil chaperonin GroEL (cpn 60) with the ATP ana logue 2',3' oxidised ATP (oATP) has been studied. Treatment with the r eagent leads to loss of the ATPase activity of GroEL in a pseudo-first -order fashion; this can be prevented by inclusion of ATP in the react ion mixture. Measurements of the stoichiometry of the reaction indicat e that the loss of activity corresponds to the incorporation of about one oATP per subunit of GroEL. From analysis of the sequences of modif ied peptides it is proposed that the reaction probably occurs with one or both of the two cysteines Cys-457 and Cys-518, although the instab ility of the adduct(s) makes a definite identification of the site(s) of reaction difficult. The involvement of Cys side chains in the react ion with oATP was confirmed by using Nbs, (5,5'-dithiobis(2-nitrobenzo ate)) to estimate thiol groups in both modified and unmodified GroEL.