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The X‐ray structure of the NAD‐dependent 5,10‐methylenetetrahydrofolate dehydrogenase from Saccharomyces cerevisiae
Author(s) -
Monzingo Arthur F.,
Breksa Andrew,
Ernst Stephen,
Appling Dean R.,
Robertus Jon D.
Publication year - 2000
Publication title -
protein science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.353
H-Index - 175
eISSN - 1469-896X
pISSN - 0961-8368
DOI - 10.1110/ps.9.7.1374
Subject(s) - nad+ kinase , cofactor , bifunctional , enzyme , phosphofructokinase 2 , dehydrogenase , biochemistry , stereochemistry , dimer , active site , chemistry , oxidoreductase , saccharomyces cerevisiae , biology , yeast , organic chemistry , catalysis
Eucaryotes possess one or more NADP‐dependent methylene‐THF dehydrogenases as part of multifunctional enzymes. In addition, yeast expresses an unusual monofunctional NAD‐dependent enzyme, yMTD. We report X‐ray structures for the apoenzyme and its complex with NAD + at 2.8 and 3.0 Å resolution, respectively. The protein fold resembles that seen for the human and Escherichia coli dehydrogenase/cyclohydrolase bifunctional enzymes. The enzyme has two prominent domains, with the active site cleft between them. yMTD has a noncanonical NAD‐binding domain that has two inserted strands compared with the NADP‐binding domains of the bifunctional enzymes. This insert precludes yMTD from dimerizing in the same way as the bifunctional enzymes. yMTD functions as a dimer, but the mode of dimerization is novel. It does not appear that the difference in dimerization accounts for the difference in cofactor specificity or for the loss of cyclohydrolase activity. These functional differences are probably accounted for by minor differences within the tertiary structure of the active site of the monomeric protein.