| Within the last eight years the genomes of many organisms, including humans, have been sequenced. Thousands of new hypothetical proteins whose functions are unknown have been discovered. In an attempt to determine the functions of these unknown proteins as quickly as possible, the field of structural genomics, which seeks to determine function from structure, came into being. As part of a structural genomics project, the structures of three proteins from Haemophilus influenzae: HI0257, HI0719, and HI1450, were determined by NMR spectroscopy. HI0257 has a unique fold and a distribution of charged residues that have some homology to the double-stranded RNA binding domain proteins. Studies of sequence homologues of HI0257 indicate that the proteins bind to ribosomal RNA in the 70S ribosome and may function to help regulate protein synthesis. HI0719 forms a trimer and has a fold similar to the trimeric enzyme chorismate mutase but the three putative active sites identified by homology, conservation, and ligand screening do not have homology to the active sites of any known enzymes. Ligand screening of over 100 compounds identified six small molecules, several with structural similarity to compounds in the isoleucine biosynthetic pathway, which interact with HI0719. The third protein, HI1450 has a very low pI and weak structural homology to a dsDNA mimic. The distribution of negatively charged residues on the surface of HI1450 resembles the charge distribution of dsDNA, suggesting that it is also a dsDNA mimic. The structure determination of these three proteins led to the development of new software, called NOEID, aimed at accelerating various stages of structure determination by NMR. In particular, NOEID automates the initial labeling of peaks and the assignment of NOESY restraints in NMR spectra. In addition, it provides a host of options to easily write the restraint lists used in various structure calculation programs. |
