Common themes in redox chemistry emerge from the X-ray structure of oilseed rape (Brassica napus) enoyl acyl carrier protein reductase.
BACKGROUND
Enoyl acyl carrier protein reductase (ENR) catalyzes the NAD(P)H-dependent reduction of trans-delta 2-enoyl acyl carrier protein, an essential step in de novo fatty acid biosynthesis. Plants contain both NADH-dependent and separate NADPH-dependent ENR enzymes which form part of the dissociable type II fatty acid synthetase. Highly elevated levels of the NADH-dependent enzyme are found during lipid deposition in maturing seeds of oilseed rape (Brassica napus).


RESULTS
The crystal structure of an ENR-NAD binary complex has been determined at 1.9 A resolution and consists of a homotetramer in which each subunit forms a single domain comprising a seven-stranded parallel beta sheet flanked by seven alpha helices. The subunit has a topology highly reminiscent of a dinucleotide-binding fold. The active site has been located by difference Fourier analysis of data from crystals equilibrated in NADH.


CONCLUSIONS
The structure of ENR shows a striking similarity with the epimerases and short-chain alcohol dehydrogenases, in particular, 3 alpha,20 beta-hydroxysteroid dehydrogenase (HSD). The similarity with HSD extends to the conservation of a catalytically important lysine that stabilizes the transition state and to the use of a tyrosine as a base--with subtle modifications arising from differing requirements of the reduction chemistry.
Krebs Institute for Biomolecular Research, Department of Molecular Biology and Biotechnology, University of Sheffield, UK.
J B
JB
Rafferty
J W
JW
Simon
C
C
Baldock
P J
PJ
Artymiuk
P J
PJ
Baker
A R
AR
Stuitje
A R
AR
Slabas
D W
DW
Rice
D000595:Amino Acid Sequence; D017033:Anabaena / Q000201:enzymology; D001665:Binding Sites; D001937:Brassica / Q000201:enzymology*; D017124:Conserved Sequence; D003349:Cortisone Reductase / Q000737:chemistry; D018360:Crystallography, X-Ray; D050753:Enoyl-(Acyl-Carrier-Protein) Reductase (NADH); D004926:Escherichia coli / Q000201:enzymology; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009169:Mycobacterium tuberculosis / Q000201:enzymology; D009243:NAD / Q000737:chemistry / Q000378:metabolism; D009711:Nucleotides / Q000378:metabolism; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000737:chemistry*; D011487:Protein Conformation; D017510:Protein Folding; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
D009711:Nucleotides; D009243:NAD; D010088:Oxidoreductases; D003349:Cortisone Reductase; D050753:Enoyl-(Acyl-Carrier-Protein) Reductase (NADH)