Crystal structure of the YjeE protein from Haemophilus influenzae: a putative Atpase involved in cell wall synthesis.

A hypothetical protein encoded by the gene YjeE of Haemophilus influenzae was selected as part of a structural genomics project for X-ray analysis to assist with the functional assignment. The protein is considered essential to bacteria because the gene is present in virtually all bacterial genomes but not in those of archaea or eukaryotes. The amino acid sequence shows no homology to other proteins except for the presence of the Walker A motif G-X-X-X-X-G-K-T that indicates the possibility of a nucleotide-binding protein. The YjeE protein was cloned, expressed, and the crystal structure determined by the MAD method at 1.7-A resolution. The protein has a nucleotide-binding fold with a four-stranded parallel beta-sheet flanked by antiparallel beta-strands on each side. The topology of the beta-sheet is unique among P-loop proteins and has features of different families of enzymes. Crystallization of YjeE in the presence of ATP and Mg2+ resulted in the structure with ADP bound in the P-loop. The ATPase activity of YjeE was confirmed by kinetic measurements. The distribution of conserved residues suggests that the protein may work as a "molecular switch" triggered by ATP hydrolysis. The phylogenetic pattern of YjeE suggests its involvement in cell wall biosynthesis.

Assisting functional assignment for hypothetical Heamophilus influenzae gene products through structural genomics.

The three-dimensional structures of Haemophilus influenzae proteins whose biological functions are unknown are being determined as part of a structural genomics project to ask whether structural information can assist in assigning the functions of proteins. The structures of the hypothetical proteins are being used to guide further studies and narrow the field of such studies for ultimately determining protein function. An outline of the structural genomics methodological approach is provided along with summaries of a number of completed and in progress crystallographic and NMR structure determinations. With more than twenty-five structures determined at this point and with many more in various stages of completion, the results are encouraging in that some level of functional understanding can be deduced from experimentally solved structures. In addition to aiding in functional assignment, this effort is identifying a number of possible new targets for drug development.