The crystal structure of a plant 3-ketoacyl-CoA thiolase reveals the potential for redox control of peroxisomal fatty acid beta-oxidation.
Crystal structures of peroxisomal Arabidopsis thaliana 3-ketoacyl-CoA thiolase (AtKAT), an enzyme of fatty acid beta-oxidation, are reported. The subunit, a typical thiolase, is a combination of two similar alpha/beta domains capped with a loop domain. The comparison of AtKAT with the Saccharomyces cerevisiae homologue (ScKAT) structure reveals a different placement of subunits within the functional dimers and that a polypeptide segment forming an extended loop around the open catalytic pocket of ScKAT converts to alpha-helix in AtKAT, and occludes the active site. A disulfide is formed between Cys192, on this helix, and Cys138, a catalytic residue. Access to Cys138 is determined by the structure of this polypeptide segment. AtKAT represents an oxidized, previously unknown inactive form, whilst ScKAT is the reduced and active enzyme. A high level of sequence conservation is observed, including Cys192, in eukaryotic peroxisomal, but not mitochondrial or prokaryotic KAT sequences, for this labile loop/helix segment. This indicates that KAT activity in peroxisomes is influenced by a disulfide/dithiol change linking fatty acid beta-oxidation with redox regulation.
Sundaramoorthy
Ramasubramanian
R
Division of Biological Chemistry and Molecular Microbiology, School of Life Sciences, University of Dundee, Dundee DD1 5EH, UK.
Micossi
Elena
E
Alphey
Magnus S
MS
Germain
Véronique
V
Bryce
James H
JH
Smith
Steve M
SM
Leonard
Gordon A
GA
Hunter
William N
WN
D000102:Acetyl-CoA C-Acyltransferase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D017360:Arabidopsis / Q000201:enzymology; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D018360:Crystallography, X-Ray; D019281:Dimerization; D005227:Fatty Acids / Q000737:chemistry*; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D020675:Peroxisomes / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment
D029681:Arabidopsis Proteins; D005227:Fatty Acids; D021122:Protein Subunits; D029701:Saccharomyces cerevisiae Proteins; D000102:Acetyl-CoA C-Acyltransferase