Biomedical subjects

M L Weng

Publications and source records attributed to M L Weng.

3 recordsLinked to original sources

PubMed2001

[lambda N gene expression regulated by the leader sequence].

It was reported recently that changing the TIR (translational initiation region) of lambda N gene resulted in the increasing expression of lambda N gene and it was regulated at translational level. According to the alignment, the leader sequence of lambda N gene had three parts: a code region for ORF lambda N, the upstream sequence of ORF lambda N and 17 bp of spacer between ORF lambda N and downstream of lambda N gene. ORF lambda N is an open reading frame located at upstream of lambda N gene coding a peptide of 19 amino acids. To study the mechanism of regulation of lambda N gene expression, three serials of plasmids with mutant leader region of lambda N gene were constructed. (1) pMC1403-XT, in which the start codon or the partial code of ORF lambda N was connected with lacZ to obtain the ORF lambda N-lacZ fusion gene and in which the ORF lambda N-lacZ expression was under the control of a strong trp/lac promoter; (2) The ORF lambda N mutants in which the termination codon TAA was introduced into ORF lambda N at different positions by site-directed mutagenesis to preterminate the ORF lambda N on plasmid pMC1403N; (3) Mutants in which a deletion was located at upstream ORF lambda N in the ORF lambda N mutants above. The results obtained from determination of the beta-galactosidase activity in the transformants harboring the different plasmids showed that the ORF lambda N-lacZ expression was suppressed by the ORF lambda N code region and the lambda N expression was increased in both the second and third serials of mutants. At the same time the results from RNA-DNA dot hybridization showed that the lambda N gene expression was regulated at translational level. Therefore it was predicted that the reason of relatively low expression for lambda N gene in pMC1403N was due to the low efficiency of ORF lambda N translation. There are two ways to increase the expression of lambda N gene. One is to preterminate the translation of ORF lambda N at a suitable position to decrease the ORF lambda N effects on downstream lambda N gene translation; the other is to change the upstream sequence of ORF lambda N to improve its translation efficiency.

5' Untranslated Regions↗

PubMed2000

[AFLP analysis of photoperiod-sensitive genic male sterile(PGMS) rice mutant lines].

The reaction conditions for rice AFLP assay were optimized. The relative efficiencies for polymorphism detection of RFLP, RAPD and AFLP were compared through the analysis between a pair of PGMS allelic mutant lines(NK58S and NK58F). Results indicated that the efficiency for polymorphism detection in rice is in the order of AFLP > RAPD > RFLP, and also indicated that AFLP is a powerful DNA molecular marker technique for polymorphism detection, especially in the cases of extremely low polymorphism, such as isogeneic lines and allelic mutant lines. The advantages and disadvantages of these three molecular marker systems were discussed. Using AFLP in conjunction with bulked segregating analysis, 5106 AFLP loci were screened and 9 of them showed polymorphism between NK58S and NK58F, 4 of the polymorphic AFLP products were cloned, Southern bloting analysis showed that two of them were single copy sequences while the other two were low copy sequences in rice genome.

Mutation↗

PubMed1987

Structural role for a conserved region in the CTP synthetase glutamine amide transfer domain.

Site-directed mutations were introduced into a conserved region of the Escherichia coli CTP synthetase glutamine amide transfer domain. The amino acid replacements, valine 349 to serine, glycine 351 to alanine, glycine 352 to proline, and glycine 352 to cysteine, all increased the lability of CTP synthetase. The proline 352 replacement abolished the capacity to form the covalent glutaminyl-cysteine 379 catalytic intermediate, thus preventing glutamine amide transfer function; NH3-dependent CTP synthetase activity was retained. In CTP synthetase (serine 349), both glutamine and NH3-dependent activities were increased approximately 30% relative to that of the wild type. CTP synthetase mutants alanine 351 and cysteine 352 were not overproduced because of apparent instability and proteolytic degradation. We conclude that the conserved region between residues 346 and 355 in the CTP synthetase glutamine amide transfer domain has an important structural role.

Affinity Labels↗