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Isolation, characterization, and expression of the Corynebacterium glutamicum betP gene, encoding the transport system for the compatible solute glycine betaine.

ABSTRACT: Corynebacterium glutamicum accumulates glycine betaine under conditions of high osmolarity. Previous work revealed the existence of a high-affinity glycine betaine permease which is osmotically regulated. In the present study, the corresponding gene was cloned. The betP gene, encoding the glycine betaine uptake carrier, was isolated by heterologous complementation of mutant strain Escherichia coli MKH13. From sequence analysis it is predicted to encode a protein of 595 amino acids. This protein shares 36% identity with the choline transport system BetT and 28% identity with the carnitine transport system CaiT of E. coli, as well as 38% identity with a protein with an unknown function from Haemophilus influenzae. Analysis of hydropathy indicated a common structure for all four transport proteins. After heterologous expression of betP in E. coli MKH13, the measured Km values for glycine betaine and the cotransported Na+ were similar to those found in C. glutamicum, whereas the modulation of activity by osmotic gradients was shifted to lower osmotic values.

SUBMITTER: Peter H

PROVIDER: S-EPMC178321 | biostudies-other | 1996 Sep

REPOSITORIES: biostudies-other

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Isolation, characterization, and expression of the Corynebacterium glutamicum betP gene, encoding the transport system for the compatible solute glycine betaine.

Peter H H Burkovski A A Krämer R R

Journal of bacteriology 19960901 17

Corynebacterium glutamicum accumulates glycine betaine under conditions of high osmolarity. Previous work revealed the existence of a high-affinity glycine betaine permease which is osmotically regulated. In the present study, the corresponding gene was cloned. The betP gene, encoding the glycine betaine uptake carrier, was isolated by heterologous complementation of mutant strain Escherichia coli MKH13. From sequence analysis it is predicted to encode a protein of 595 amino acids. This protein ...[more]

PMID: 8752342

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Project description:?-D-Glucosylglycerol (?GG) has beneficial functions as a moisturizing agent in cosmetics and potential as a health food material, and therapeutic agent. ?GG serves as compatible solute in various halotolerant cyanobacteria such as Synechocystis sp. PCC 6803, which synthesizes ?GG in a two-step reaction: The enzymatic condensation of ADP-glucose and glycerol 3-phosphate by GG-phosphate synthase (GGPS) is followed by the dephosphorylation of the intermediate by the GG-phosphate phosphatase (GGPP). The Gram-positive Corynebacterium glutamicum, an industrial workhorse for amino acid production, does not utilize ?GG as a substrate and was therefore chosen for the development of a heterologous microbial production platform for ?GG.Plasmid-bound expression of ggpS and ggpP from Synechocystis sp. PCC 6803 enabled ?GG synthesis exclusively in osmotically stressed cells of C. glutamicum (pEKEx2-ggpSP), which is probably due to the unique intrinsic control mechanism of GGPS activity in response to intracellular ion concentrations. C. glutamicum was then engineered to optimize precursor supply for ?GG production: The precursor for ?GG synthesis ADP-glucose gets metabolized by both the glgA encoded glycogen synthase and the otsA encoded trehalose-6-phosphate synthase. Upon deletion of both genes the ?GG concentration in culture supernatants was increased from 0.5 mM in C. glutamicum (pEKEx3-ggpSP) to 2.9 mM in C. glutamicum ?otsA IMglgA (pEKEx3-ggpSP). Upon nitrogen limitation, which inhibits synthesis of amino acids as compatible solutes, C. glutamicum ?otsA IMglgA (pEKEx3-ggpSP) produced more than 10 mM ?GG (about 2 g L-1).Corynebacterium glutamicum can be engineered as efficient platform for the production of the compatible solute ?GG. Redirection of carbon flux towards ?GG synthesis by elimination of the competing pathways for glycogen and trehalose synthesis as well as optimization of nitrogen supply is an efficient strategy to further optimize production of ?GG.

Dataset Information

Isolation, characterization, and expression of the Corynebacterium glutamicum betP gene, encoding the transport system for the compatible solute glycine betaine.

Publications

Isolation, characterization, and expression of the Corynebacterium glutamicum betP gene, encoding the transport system for the compatible solute glycine betaine.

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