title: Structure of the adenylation-peptidyl carrier protein didomain of the Microcystis aeruginosa microcystin synthetase McyG.
abstract: Microcystins, which are the most common cause of hepatotoxicity associated with cyanobacterial water blooms, are assembled in vivo on a large multienzyme complex via a mixed nonribosomal peptide synthetase/polyketide synthetase (NRPS/PKS). The biosynthesis of microcystin in Microcystis aeruginosa PCC 7806 starts with the enzyme McyG, which contains an adenylation-peptidyl carrier protein (A-PCP) didomain for loading the starter unit to assemble the side chain of an Adda residue. However, the catalytic mechanism remains unclear. Here, the 2.45 Å resolution crystal structure of the McyG A-PCP didomain complexed with the catalytic intermediate L-phenylalanyl-adenylate (L-Phe-AMP) is reported. Each asymmetric unit contains two protein molecules, one of which consists of the A-PCP didomain and the other of which comprises only the A domain. Structural analyses suggest that Val227 is likely to be critical for the selection of hydrophobic substrates. Moreover, two distinct interfaces demonstrating variable crosstalk between the PCP domain and the A domain were observed. A catalytic cycle for the adenylation and peptide transfer of the A-PCP didomain is proposed.
authors: Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230027, People's Republic of China.
authors: Xiao-Feng
authors: XF
authors: Tan
authors: Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230027, People's Republic of China.
authors: Ya-Nan
authors: YN
authors: Dai
authors: Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230027, People's Republic of China.
authors: Kang
authors: K
authors: Zhou
authors: Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230027, People's Republic of China.
authors: Yong-Liang
authors: YL
authors: Jiang
authors: Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230027, People's Republic of China.
authors: Yan-Min
authors: YM
authors: Ren
authors: Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230027, People's Republic of China.
authors: Yuxing
authors: Y
authors: Chen
authors: Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230027, People's Republic of China.
authors: Cong-Zhao
authors: CZ
authors: Zhou
mesh_terms: D000595:Amino Acid Sequence; D018360:Crystallography, X-Ray; D008025:Ligases / Q000737:chemistry* / Q000378:metabolism; D052998:Microcystins / Q000378:metabolism*; D046931:Microcystis / Q000737:chemistry / Q000201:enzymology* / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment
chemical_list: D052998:Microcystins; C078588:microcystin; D008025:Ligases
keywords: McyG; NRPS/PKS; adenylation–peptidyl carrier protein didomain; microcystin; reaction cycle