Crystallographic structure and substrate-binding interactions of the molybdate-binding protein of the phytopathogen Xanthomonas axonopodis pv. citri.
In Xanthomonas axonopodis pv. citri (Xac or X. citri), the modA gene codes for a periplasmic protein (ModA) that is capable of binding molybdate and tungstate as part of the ABC-type transporter required for the uptake of micronutrients. In this study, we report the crystallographic structure of the Xac ModA protein with bound molybdate. The Xac ModA structure is similar to orthologs with known three-dimensional structures and consists of two nearly symmetrical domains separated by a hinge region where the oxyanion-binding site lies. Phylogenetic analysis of different ModA orthologs based on sequence alignments revealed three groups of molybdate-binding proteins: bacterial phytopathogens, enterobacteria and soil bacteria. Even though the ModA orthologs are segregated into different groups, the ligand-binding hydrogen bonds are mostly conserved, except for Archaeglobus fulgidus ModA. A detailed discussion of hydrophobic interactions in the active site is presented and two new residues, Ala38 and Ser151, are shown to be part of the ligand-binding pocket.
Balan
Andrea
A
Departamento de Microbiologia, Instituto de Ciências Biomédicas II, Universidade de São Paulo, Cidade Universitária, São Paulo, SP, 05008-900, Brazil.
Santacruz-Pérez
Carolina
C
Moutran
Alexandre
A
Ferreira
Luís Carlos Souza
LC
Neshich
Goran
G
Gonçalves Barbosa
João Alexandre Ribeiro
JA
D000595:Amino Acid Sequence; D001665:Binding Sites; D017124:Conserved Sequence; D018360:Crystallography, X-Ray; D008024:Ligands; D008969:Molecular Sequence Data; D008982:Molybdenum / Q000737:chemistry* / Q000378:metabolism*; D033902:Periplasmic Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D010802:Phylogeny; D010935:Plant Diseases / Q000382:microbiology; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D040681:Structural Homology, Protein; D053532:Xanthomonas axonopodis / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity
D008024:Ligands; D033902:Periplasmic Binding Proteins; C044659:molybdate; D008982:Molybdenum