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Transcribed sequences of the Escherichia coli btuB gene control its expression and regulation by vitamin B12.

ABSTRACT: The Escherichia coli btuB gene product is an outer membrane protein required for the active transport of vitamin B12 and other cobalamins. Synthesis of BtuB is repressed when cells are grown in the presence of cobalamins. Mapping of the 5' end of the btuB transcript revealed that a 240-nucleotide transcribed leader precedes the coding sequence. Point mutations causing increased expression under repressing conditions were isolated by use of a btuB-lacZ gene fusion. Mutations at many sites within the leader region affected btuB-lacZ regulation, whereas some base changes upstream of the start of transcription affected the absolute level of expression but not its repressibility. Analysis of btuB-phoA gene fusions and btuB-lacZ operon and gene fusions of various lengths showed that sequences within the btuB coding region (between nucleotides +250 and +350) had to be present for proper expression and transcriptional regulation. Sequences within the leader region (up to +250) conferred regulation of translational fusions. These results indicate that btuB expression is controlled at both the transcriptional and translational levels and that different but possibly overlapping sequences in the transcribed region, including the coding region for the transport protein itself, mediate these two modes of regulation.

SUBMITTER: Lundrigan MD

PROVIDER: S-EPMC51042 | biostudies-other | 1991 Feb

REPOSITORIES: biostudies-other

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Transcribed sequences of the Escherichia coli btuB gene control its expression and regulation by vitamin B12.

Lundrigan M D MD Köster W W Kadner R J RJ

Proceedings of the National Academy of Sciences of the United States of America 19910201 4

The Escherichia coli btuB gene product is an outer membrane protein required for the active transport of vitamin B12 and other cobalamins. Synthesis of BtuB is repressed when cells are grown in the presence of cobalamins. Mapping of the 5' end of the btuB transcript revealed that a 240-nucleotide transcribed leader precedes the coding sequence. Point mutations causing increased expression under repressing conditions were isolated by use of a btuB-lacZ gene fusion. Mutations at many sites within ...[more]

PMID: 1847525

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Project description:BackgroundVitamin B12 is an essential micronutrient in humans needed for health maintenance. Deficiency of vitamin B12 has been linked to dietary, environmental and genetic factors. Evidence for the genetic basis of vitamin B12 status is poorly understood. However, advancements in genomic techniques have increased the knowledge-base of the genetics of vitamin B12 status. Based on the candidate gene and genome-wide association (GWA) studies, associations between genetic loci in several genes involved in vitamin B12 metabolism have been identified.ObjectiveThe objective of this literature review was to identify and discuss reports of associations between single-nucleotide polymorphisms (SNPs) in vitamin B12 pathway genes and their influence on the circulating levels of vitamin B12.MethodsRelevant articles were obtained through a literature search on PubMed through to May 2017. An article was included if it examined an association of a SNP with serum or plasma vitamin B12 concentration. Beta coefficients and odds ratios were used to describe the strength of an association, and a P < 0.05 was considered as statistically significant. Two reviewers independently evaluated the eligibility for the inclusion criteria and extracted the data.ResultsFrom 23 studies which fulfilled the selection criteria, 16 studies identified SNPs that showed statistically significant associations with vitamin B12 concentrations. Fifty-nine vitamin B12-related gene polymorphisms associated with vitamin B12 status were identified in total, from the following populations: African American, Brazilian, Canadian, Chinese, Danish, English, European ancestry, Icelandic, Indian, Italian, Latino, Northern Irish, Portuguese and residents of the USA.ConclusionOverall, the data analyzed suggests that ethnic-specific associations are involved in the genetic determination of vitamin B12 concentrations. However, despite recent success in genetic studies, the majority of identified genes that could explain variation in vitamin B12 concentrations were from Caucasian populations. Further research utilizing larger sample sizes of non-Caucasian populations is necessary in order to better understand these ethnic-specific associations.

Dataset Information

Transcribed sequences of the Escherichia coli btuB gene control its expression and regulation by vitamin B12.

Publications

Transcribed sequences of the Escherichia coli btuB gene control its expression and regulation by vitamin B12.

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