title: Crystal structure of a bifunctional aldolase-dehydrogenase: sequestering a reactive and volatile intermediate.
abstract: The crystal structure of the bifunctional enzyme 4-hydroxy-2-ketovalerate aldolase (DmpG)/acylating acetaldehyde dehydrogenase (DmpF), which is involved in the bacterial degradation of toxic aromatic compounds, has been determined by multiwavelength anomalous dispersion (MAD) techniques and refined to 1.7-A resolution. Structures of the two polypeptides represent a previously unrecognized subclass of metal-dependent aldolases, and of a CoA-dependent dehydrogenase. The structure reveals a mixed state of NAD+ binding to the DmpF protomer. Domain movements associated with cofactor binding in the DmpF protomer may be correlated with channeling and activity at the DmpG protomer. In the presence of NAD+ a 29-A-long sequestered tunnel links the two active sites. Two barriers are visible along the tunnel and suggest control points for the movement of the reactive and volatile acetaldehyde intermediate between the two active sites.
authors.affiliation: Department of Molecular, Cellular and Developmental Biology Sinsheimer Laboratory, 1156 High Street, University of California, Santa Cruz, CA 95064, USA.
authors.forename: Babu A
authors.initials: BA
authors.lastname: Manjasetty
authors.forename: Justin
authors.initials: J
authors.lastname: Powlowski
authors.forename: Alice
authors.initials: A
authors.lastname: Vrielink
mesh_terms: D000079:Acetaldehyde / Q000378:metabolism; D000445:Aldehyde Oxidoreductases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D009243:NAD / Q000378:metabolism; D007652:Oxo-Acid-Lyases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011487:Protein Conformation; D020836:Protein Structure, Quaternary; D011549:Pseudomonas / Q000201:enzymology / Q000235:genetics; D012997:Solvents; D055672:Static Electricity
chemical_list: D012997:Solvents; D009243:NAD; D000445:Aldehyde Oxidoreductases; C027014:acetaldehyde dehydrogenase (acylating); C038482:4-hydroxy-2-ketovalerate aldolase; D007652:Oxo-Acid-Lyases; D000079:Acetaldehyde