The structure of L-tyrosine 2,3-aminomutase from the C-1027 enediyne antitumor antibiotic biosynthetic pathway.
The SgcC4 l-tyrosine 2,3-aminomutase (SgTAM) catalyzes the formation of (S)-beta-tyrosine in the biosynthetic pathway of the enediyne antitumor antibiotic C-1027. SgTAM is homologous to the histidine ammonia lyase family of enzymes whose activity is dependent on the methylideneimidazole-5-one (MIO) cofactor. Unlike the lyase enzymes, SgTAM catalyzes additional chemical transformations resulting in an overall stereospecific 1,2-amino shift in the substrate l-tyrosine to generate (S)-beta-tyrosine. Previously, we provided kinetic, spectroscopic, and mutagenesis data supporting the presence of MIO in the active site of SgTAM [Christenson, S. D.; Wu, W.; Spies, A.; Shen, B.; and Toney, M. D. (2003) Biochemistry 42, 12708-12718]. Here we report the first X-ray crystal structure of an MIO-containing aminomutase, SgTAM, and confirm the structural homology of SgTAM to ammonia lyases. Comparison of the structure of SgTAM to the l-tyrosine ammonia lyase from Rhodobacter sphaeroides provides insight into the structural basis for aminomutase activity. The results show that SgTAM has a closed active site well suited to retain ammonia and minimize the formation of lyase elimination products. The amino acid determinants for substrate recognition and catalysis can be predicted from the structure, setting the framework for detailed mechanistic investigations.
Christianson
Carl V
CV
Department of Chemistry, Boston College, Eugene F. Merkert Chemistry Center, Chestnut Hill, Massachusetts 02467, USA.
Montavon
Timothy J
TJ
Van Lanen
Steven G
SG
Shen
Ben
B
Bruner
Steven D
SD
D000595:Amino Acid Sequence; D000617:Aminoglycosides / Q000096:biosynthesis*; D000903:Antibiotics, Antineoplastic / Q000096:biosynthesis*; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D053281:Enediynes; D007093:Imidazoles / Q000737:chemistry / Q000378:metabolism; D019751:Intramolecular Transferases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D020836:Protein Structure, Quaternary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D055672:Static Electricity; D013302:Streptomyces / Q000201:enzymology / Q000235:genetics
D000617:Aminoglycosides; D000903:Antibiotics, Antineoplastic; D053281:Enediynes; D007093:Imidazoles; D011994:Recombinant Proteins; C447541:methylidene-imidazolone; C058024:C 1027; D019751:Intramolecular Transferases; C023206:tyrosine 2,3-aminomutase