Analysis of the levels of conservation of the J domain among the various types of DnaJ-like proteins

DnaJ-like proteins are defined by the presence of an approximately 73 amino acid region termed the J domain. This region bears similarity to the initi al 73 amino acids of the Escherichia coli protein DnaJ. Although the struct ures of the J domains of E coli DnaJ and human heat shock protein 40 have b een solved using nuclear magnetic resonance, no detailed analysis of the am ino acid conservation among the J domains of the various DnaJ-like proteins has yet been attempted. A multiple alignment of 223 J domain sequences was performed, and the levels of amino acid conservation at each position were established. It was found that the levels of sequence conservation were pa rticularly high in 'true' DnaJ homologues (ie, those that share full domain conservation with DnaJ) and decreased substantially in those J domains in DnaJ-like proteins that contained no additional similarity to DnaJ outside their J domain. Residues were also identified that could be important for s tabilizing the J domain and for mediating the interaction with heat shock p rotein 70.