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A brief introduction to the genome databases GDB, GenoList and Ensembl is given. These databases, mirrored and maintained at the Centre of Bioinformatics, Peking University, provide useful information for genome research.

Based on a predicted three-dimensional structure of hypoxanthine-guanine phosphoribosyltransferase (HGPRT) from Thermoanaerobacter tengcongensis, three mutants of HGPRT were designed to modify the purine specificity of HGPRT. Site-directed mutagenesis was used to generate the three mutants, K(133)A, K(133)S, K(133)T. Wild type HGPRT and its mutants were expressed E. coli in BL21 (DE3) pLysS, and the expression products of them reached about 30% of the total protein. The molecular weight of the recombinant proteins was 22 kD. The specific activities of the enzymes were determined. Catalytic activities of mutants K(133)A, K(133)S, K(133)T retained only 4%, 1.1%, 2.7% activities, respectively, of the wild type for hypoxanthine, 1.7% 0.6% 1% activities, respectively, of wild type for guanine. However, the three mutants showed 24-fold, 7-fold, 18-fold activities, respectively, of the wild type for xanthine, and 650-fold, 210-fold, 380-fold activities, respectively, of the wild type for adenine. Comparison of kinetic data for purified recombinant mutant with wild-type HGPRT showed significant difference in the catalytic efficiency (kcat/Km) for purine, xanthine and adenine, the mutants exhibiting more than 40 to 50-fold higher kcat/Km, as a result of nearly 4 to 5-fold decrease in Km, compared with wild-type. These results demonstrate that a single amino acid substitution in HGPRT at the active site can significantly modify the specificity for binding purine.

Multiple sequence alignment among 12 complete SARS coronavirus (SARS-CoV) sequences reveals that the major parts of 29708 b of the genomes have 99.82% identical bases. Forty two nucleotide mismatches were found in addition to the five and six gaps in two genomes. Among them, 28 mismatches result in changes of amino acid in the encoded proteins. Analysis of the changes implies possible effect on the Spike and Membrane protein of the virus, while most of the other changes seem not very significant to alter the structure and function of the proteins. These results have been released on the anti-sars web site maintained by the Centre of Bioinformatics, Peking University (antisars.cbi.pku.edu.cn) and may be of help for further experimental study.

Huwentoxin-II (HWTX-II)is an insecticidal peptide purified from the venom of spider Selenocosmia huwena. The structure of this toxin in solution was investigated using 2D-NMR. The complete sequence-specific assignments of proton resonance in the (1)H-NMR spectra of HWTX-II were obtained by analyzing a series of 2D spectrum, including COSY, DQF-COSY, TOCSY and NOESY. All the backbone protons and side chain protons, except epsilonNH(2) protons of Lys residues, were identified by d(alphaN), d(alphadgr);, d(NN) and d(betaN) connectivities. The results provide a basis for further determination of the solution conformation of HWTX-II. Furthermore the secondary structure of HWTX-II was determined from NMR data. It contained mainly extended conformation, especially a double-stranded anti-parallel beta-sheet with Trp27--Cys29 and Cys34--Lys36 at the C terminal, and it lacked helix. These characters of the secondary structure of HWTX-II were similar to those spider toxins which structure in solution had been reported.