4QUV

Structure of an integral membrane delta(14)-sterol reductase

Summary for 4QUV

• Entry DOI: 10.2210/pdb4quv/pdb
• Descriptor: Delta(14)-sterol reductase, NADPH DIHYDRO-NICOTINAMIDE-ADENINE-DINUCLEOTIDE PHOSPHATE (2 entities in total)
• Functional Keywords: membrane protein, cholesterol biosynthesis, oxidoreductase
• Biological source: Methylomicrobium alcaliphilum
• Total number of polymer chains: 2
• Total formula weight: 100424.07

Authors

Li, X.,Blobel, G. (deposition date: 2014-07-12, release date: 2014-10-08, Last modification date: 2024-02-28)

Primary citation

Li, X.,Roberti, R.,Blobel, G.
Structure of an integral membrane sterol reductase from Methylomicrobium alcaliphilum.
Nature, 517:104-107, 2015

PubMed Abstract: Sterols are essential biological molecules in the majority of life forms. Sterol reductases including Δ(14)-sterol reductase (C14SR, also known as TM7SF2), 7-dehydrocholesterol reductase (DHCR7) and 24-dehydrocholesterol reductase (DHCR24) reduce specific carbon-carbon double bonds of the sterol moiety using a reducing cofactor during sterol biosynthesis. Lamin B receptor (LBR), an integral inner nuclear membrane protein, also contains a functional C14SR domain. Here we report the crystal structure of a Δ(14)-sterol reductase (MaSR1) from the methanotrophic bacterium Methylomicrobium alcaliphilum 20Z (a homologue of human C14SR, LBR and DHCR7) with the cofactor NADPH. The enzyme contains ten transmembrane segments (TM1-10). Its catalytic domain comprises the carboxy-terminal half (containing TM6-10) and envelops two interconnected pockets, one of which faces the cytoplasm and houses NADPH, while the other one is accessible from the lipid bilayer. Comparison with a soluble steroid 5β-reductase structure suggests that the reducing end of NADPH meets the sterol substrate at the juncture of the two pockets. A sterol reductase activity assay proves that MaSR1 can reduce the double bond of a cholesterol biosynthetic intermediate, demonstrating functional conservation to human C14SR. Therefore, our structure as a prototype of integral membrane sterol reductases provides molecular insight into mutations in DHCR7 and LBR for inborn human diseases.

PubMed: 25307054
DOI: 10.1038/nature13797

Experimental method

X-RAY DIFFRACTION (2.743 Å)