Mutation spectrum of phenylketonuria in Iranian population.

Identification of molecular basis of phenylketonuria (PKU) in Iran has been accomplished through the analysis of 248 unrelated chromosomes from 124 Iranian classic PKU subjects. Phenylalanine hydroxylase (PAH) gene mutations were analyzed through a combined approach in which p.S67P, p.R252W, p.R261Q, p.R261X, p.L333F, IVS10-11G>A, IVS11+1G>C, p.L364del, p.R408Q and p.R408W mutations were first screened by PCR of PAH gene exons 3, 7, 10, 11 and 12, followed by digestion with the appropriate digestion enzymes. Subsequently SSCP analysis for exons 2, 6, 7 and 11 of the PAH gene and finally, sequencing of 13 PAH gene exons have been used to study uncharacterized PKU chromosomes. 26 different mutations were found. The predominant mutation in this population sample was IVS10-11G>A, with a frequency of 24.6%. Nine mutations (IVS10-11G>A, p.R261Q, p.P281L, IVS11+1G>C, p.K363>NFS, p.R243X, IVS2+5G>C, p.R261X and p.R252W) represent almost 84% of all PKU chromosomes studied. IVS10-11G>A mutation is the major PKU-causing mutation throughout the Mediterranean region. The finding of the high prevalence of this mutation in Iranian population is consistent with the historical and geographical links between Iranian and Mediterranean populations.

Carrier detection of phenylketonuria in Iranian families by variable number tandem-repeat polymorphism analysis.

This study of Iranian families assessed the usefulness of carrier detection of phenylketonuria by variable number tandem-repeat (VNTR) polymorphism analysis. We studied 171 people (45 unrelated PKU subjects, and their parents and unaffected siblings). Of 342 chromosomes (131 non-PKU and 211 PKU), 5 VNTR alleles were identified. This VNTR system would yield a polymorphism information content of 66%, comparable to that in Europeans and higher than in Chinese. Carrier detection by segregation analysis of VNTR was informative in 89.5% of siblings. We conclude that this polymorphism is highly informative in carrier detection of PKU in the Iranian population.

Carrier detection of phenylketonuria in Iranian families by variable number tandem-repeat polymorphism analysis

This study of Iranian families assessed the usefulness of carrier detection of phenylketonuria by variable number tandem-repeat [VNTR] polymorphism analysis. We studied 171 people [45 unrelated PKU subjects, and their parents and unaffected siblings]. Of 342 chromosomes [131 non-PKU and 211 PKU], 5 VNTR alleles were identified. This VNTR system would yield a polymorphism information content of 66%, comparable to that in Europeans and higher than in Chinese. Carrier detection by segregation analysis of VNTR was informative in 89.5% of siblings. We conclude that this polymorphism is highly informative in carrier detection of PKU in the Iranian population

Recovery of active beta-lactamases from Proteus vulgaris and RTEM-1 hybrid by random mutagenesis by using a dnaQ strain of Escherichia coli.

Proteus vulgaris and RTEM-1 beta-lactamases that belong to molecular class A with 37% amino acid similarity were examined to find the relationship between amino acid residues and activity of enzymes. MICs of ampicillin were > 2,000 micrograms/ml for Escherichia coli cells producing these enzymes. We have made 18 hybrid genes by substituting the coding region of the P. vulgaris beta-lactamase gene with the equivalent portions from the RTEM-1 gene. Most of these hybrids produced inactive proteins, but a few hybrid enzymes had partial or trace activity. From one of the hybrid genes (MIC of ampicillin, 100 micrograms/ml), we recovered three kinds of active mutants which provided ampicillin MICs of 1,000 micrograms/ml by the selection of spontaneous mutations in a dnaQ strain of E. coli. In these mutants, Leu-148, Met-182, and Tyr-274 were replaced with Val, Thr, and His, respectively. These amino acids have not been identified as residues with functional roles in substrate hydrolysis. Furthermore, from these hybrid mutants, we obtained a second set of mutants which conferred ampicillin MICs of 1,500 micrograms/ml. Interestingly, the second mutations were limited to these three amino acid substitutions. These amino acid residues which do not directly interact with substrates have an effect on enzyme activity. These mutant enzymes exhibited lower K(m) values for cephaloridine than both parental enzymes.

Antifungal azoxybacilin exhibits activity by inhibiting gene expression of sulfite reductase.

Azoxybacilin, produced by Bacillus cereus, has a broad spectrum of antifungal activity in methionine-free medium and has been suggested to inhibit sulfite fixation. We have further investigated the mode of action by which azoxybacilin kills fungi. The compound inhibited the incorporation of [35S] sulfate into acid-insoluble fractions of Saccharomyces cerevisiae under conditions in which virtually no inhibition was observed for DNA, RNA, or protein synthesis. It did not interfere with the activity of the enzymes for sulfate assimilation but clearly inhibited the induction of those enzymes when S. cerevisiae cells were transferred from rich medium to a synthetic methionine-free medium. Particularly strong inhibition was observed in the induction of sulfite reductase. Northern (RNA) analysis revealed that azoxybacilin decreased the level of mRNA of genes for sulfate assimilation, including MET10 for sulfite reductase and MET4, the transactivator of MET10 and other sulfate assimilation genes. When activities of azoxybacilin were compared for mRNA and enzyme syntheses from MET10, the concentration required for inhibition of transcription of the gene was about 10 times higher (50% inhibitory concentration = 30 micrograms/ml) than that required for inhibition of induction of enzyme synthesis (50% inhibitory concentration = 3 micrograms/ml). The data suggest that azoxybacilin acts on at least two steps in the expression of sulfite reductase; the transcriptional activation of MET4 and a posttranscriptional regulation in MET10 expression. We conclude that azoxybacilin exhibits antifungal activity by interfering with the regulation of expression of sulfite reductase activity.

Cloning and sequencing of sulfite reductase alpha subunit gene from Saccharomyces cerevisiae.

A DNA fragment of 2.1 kb was specifically amplified by PCR with primers based on the amino acid sequences obtained from the N-terminal region and the cyanogen bromide-derived peptide of the sulfite reductase alpha subunit in Saccharomyces cerevisiae. With this fragment as a probe, the gene coding for the sulfite reductase alpha subunit was isolated from a genomic library of S. cerevisiae. Sequencing analysis revealed that the gene contains a 3105-bp open reading frame, which is large enough to code for a protein of 1035 amino acid residues. The transcript of the sulfite reductase alpha subunit gene was detected by Northern analysis after methionine deprivation, but the amount of the transcript did not directly correlate with the enzyme activity. The DNA fragment containing the sulfite reductase alpha subunit gene rescued the met10 phenotype by complementation.