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Crystal structure of an active form of BACE1, an enzyme responsible for amyloid beta protein production.

ABSTRACT: BACE1 (beta-secretase) is a transmembrane aspartic protease that cleaves the beta-amyloid precursor protein and generates the amyloid beta peptide (Abeta). BACE1 cycles between the cell surface and the endosomal system many times and becomes activated interconvertibly during its cellular trafficking, leading to the production of Abeta. Here we report the crystal structure of the catalytically active form of BACE1. The active form has novel structural features involving the conformation of the flap and subsites that promote substrate binding. The functionally essential residues and water molecules are well defined and play a key role in the iterative activation of BACE1. We further describe the crystal structure of the dehydrated form of BACE1, showing that BACE1 activity is dependent on the dynamics of a catalytically required Asp-bound water molecule, which directly affects its catalytic properties. These findings provide insight into a novel regulation of BACE1 activity and elucidate how BACE1 modulates its activity during cellular trafficking.

SUBMITTER: Shimizu H

PROVIDER: S-EPMC2423307 | biostudies-literature | 2008 Jun

REPOSITORIES: biostudies-literature

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Crystal structure of an active form of BACE1, an enzyme responsible for amyloid beta protein production.

Shimizu Hideaki H Tosaki Asako A Kaneko Kumi K Hisano Tamao T Sakurai Takashi T Nukina Nobuyuki N

Molecular and cellular biology 20080331 11

BACE1 (beta-secretase) is a transmembrane aspartic protease that cleaves the beta-amyloid precursor protein and generates the amyloid beta peptide (Abeta). BACE1 cycles between the cell surface and the endosomal system many times and becomes activated interconvertibly during its cellular trafficking, leading to the production of Abeta. Here we report the crystal structure of the catalytically active form of BACE1. The active form has novel structural features involving the conformation of the fl ...[more]

PMID: 18378702

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Project description:Propionibacterium freudenreichii is a food grade bacterium that has gained attention as a producer of appreciable amounts of cobalamin, a cobamide with activity of vitamin B12. Production of active form of vitamin is a prerequisite for attempts to naturally fortify foods with B12 by microbial fermentation. Active vitamin B12 is distinguished from the pseudovitamin by the presence of 5,6-dimethylbenzimidazole (DMBI) as the lower ligand. Genomic data indicate that P. freudenreichii possesses a fusion gene, bluB/cobT2, coding for a predicted phosphoribosyltransferase/nitroreductase, which is presumably involved in production of vitamin B12. Understanding the mechanisms affecting the synthesis of different vitamin forms is useful for rational strain selection and essential for engineering of strains with improved B12 production properties.Here, we investigated the activity of heterologously expressed and purified fusion enzyme BluB/CobT2. Our results show that BluB/CoBT2 is responsible for the biosynthesis of the DMBI base and its activation into ?-ribazole phosphate, preparing it for attachment as the lower ligand of cobalamin. The fusion enzyme was found to be efficient in metabolite channeling and the enzymes' inability to react with adenine, a lower ligand present in the pseudovitamin, revealed a mechanism favoring the production of the active form of the vitamin. P. freudenreichii did not produce cobalamin under strictly anaerobic conditions, confirming the requirement of oxygen for DMBI synthesis. In vivo experiments also revealed a clear preference for incorporating DMBI over adenine into cobamide under both microaerobic and anaerobic conditions.The herein described BluB/CobT2 is responsible for the production and activation of DMBI. Fusing those two activities results in high pressure towards production of the true vitamin B12 by efficiently activating DMBI formed within the same enzymatic complex. This indicates that BluB/CobT2 is the crucial enzyme in the B12 biosynthetic pathway of P. freudenreichii. The GRAS organism status and the preference for synthesizing active vitamin form make P. freudenreichii a unique candidate for the in situ production of vitamin B12 within food products.

Dataset Information

Crystal structure of an active form of BACE1, an enzyme responsible for amyloid beta protein production.

Publications

Crystal structure of an active form of BACE1, an enzyme responsible for amyloid beta protein production.

Similar Datasets

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