  Ahmad et al. recently presented an NMR-based model for a bacterial DnaJ J
domain:DnaK(Hsp70):ADP complex(1) that differs significantly from the crystal
structure of a disulfide linked mammalian auxilin J domain:Hsc70 complex that
we previously published(2). They claimed that their model could better account
for existing mutational data, was in better agreement with previous NMR
studies, and that the presence of a cross-link in our structure made it
irrelevant to understanding J:Hsp70 interactions. Here we detail extensive NMR
and mutational data relevant to understanding J:Hsp70 function and show that,
in fact, our structure is much better able to account for the mutational data
and is in much better agreement with a previous NMR study of a mammalian
polyoma virus T-ag J domain:Hsc70 complex than is the Ahmad et al. complex, and
that our structure is predictive and provides insight into J:Hsp70 interactions
and mechanism of ATPase activation.

Biomolecules