CRYSTAL STRUCTURE OF L-2-HYDROXYISOCAPROATE DEHYDROGENASE FROM LACTOBACILLUS CONFUSUS AT 2.2 ANGSTROMS RESOLUTION-AN EXAMPLE OF STRONG ASYMMETRY BETWEEN SUBUNITS
Crystal structure of L-2-hydroxyisocaproate dehydrogenase from Lactobacillus confusus at 2.2 A resolution. An example of strong asymmetry between subunits.
L-2-Hydroxyisocaproate dehydrogenase (L-HicDH) from Lactobacillus confusus, a homotetramer with a molecular mass of 33 kDa per subunit, belongs to the protein family of the NAD(+)-dependent L-2-hydroxycarboxylate dehydrogenases. L-HicDH was crystallized with ammonium sulphate as precipitant in the presence of NAD+ ...
L-2-Hydroxyisocaproate dehydrogenase (L-HicDH) from Lactobacillus confusus, a homotetramer with a molecular mass of 33 kDa per subunit, belongs to the protein family of the NAD(+)-dependent L-2-hydroxycarboxylate dehydrogenases. L-HicDH was crystallized with ammonium sulphate as precipitant in the presence of NAD+. The crystals belong to the trigonal space group P3(2)21, with a = 135.9 A and c = 205.9 A, and diffract X-rays to 2.2 A resolution. The crystal structure was solved by Patterson search and molecular replacement techniques and refined to an R-value of 21.4% (2.2 to 8 A). The final structure model contains one NAD+ molecule and one sulphate ion per subunit, with 309 water molecules. An unusual feature of this crystal structure is the deviation of the protein subunits from non-crystallographic symmetry, which is so strong that it can be detected globally by self-rotation calculations in reciprocal space. This asymmetry is especially pronounced in the environment of the active site; it is reflected also in the nicotinamide conformation of NAD+ and allows some conclusions to be drawn about the catalytic mechanism. In this context, an "inner active site loop" is identified as a structural element of fundamental functional importance. Furthermore, with knowledge of the crystal structure of L-HicDH the differences in substrate specificity between L-HicDH and the L-lactate dehydrogenases can be partly explained.
Related Citations:
Deletion Variants of L-Hydroxyisocaproate Dehydrogenase-Probing Substrate Specificity Feil, I.K., Lerch, H.-P., Schomburg, D. (1994) Eur J Biochem 223: 857
Roentgenkristallographische Untersuchungen an Drei Mikrobiellen Enzymen: D-2-Hydroxyisocaproat-Dehydrogenase Aus Lactobacillus Casei, L-2-Hydroxyisocaproat-Dehydrogenase Aus Lactobacillus Confusus, Alkalische Protease Aus Bacillus Alcalophilus(Slash)Variante Q59R (German, with English Summary) Niefind, K. (1993) Thesis --: --
Cloning, Sequencing and Expression of the L-2-Hydroxyisocaproate Dehydrogenase-Encoding Gene of Lactobacillus Confusus in Escherichia Coli Lerch, H.-P., Frank, R., Collins, J. (1989) Gene 83: 263
L-2-Hydroxyisocaproate Dehydrogenase-A New Enzyme from Lactobacillus Confusus for the Stereospecific Reduction of 2-Ketocarboxylic Acids Schuette, H., Hummel, W., Kula, M.-R. (1984) Appl Microbiol Biotechnol 19: 167
Organizational Affiliation:
Gesellschaft für Biotechnologische Forschung (GBF), Abteilung Molekulare Strukturforschung, Braunschweig, Germany.
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