Crystallographic structure and substrate-binding interactions of the molybdate-binding protein of the phytopathogen...

Area of Science:

• Biochemistry
• Structural Biology
• Microbiology

Background:

• The modA gene in Xanthomonas axonopodis pv. citri encodes ModA, a periplasmic protein crucial for molybdate and tungstate uptake via an ABC-type transporter.
• Micronutrient acquisition is vital for bacterial survival and pathogenesis.

Purpose of the Study:

• To determine the crystallographic structure of the Xac ModA protein bound to molybdate.
• To elucidate the structural basis of molybdate binding and identify key residues involved.

Main Methods:

• X-ray crystallography was employed to obtain the three-dimensional structure of Xac ModA with bound molybdate.
• Phylogenetic analysis based on sequence alignments was performed on ModA orthologs.

Main Results:

• The Xac ModA structure comprises two symmetrical domains with a hinge region housing the oxyanion-binding site.
• Phylogenetic analysis classified ModA orthologs into three distinct groups: bacterial phytopathogens, enterobacteria, and soil bacteria.
• Conserved ligand-binding hydrogen bonds were observed across most orthologs, with identified hydrophobic interactions and two novel residues (Ala38, Ser151) in the binding pocket.

Conclusions:

• The determined structure provides insights into the molecular mechanism of molybdate binding by Xac ModA.
• Structural and phylogenetic analyses highlight conserved and divergent features of ModA proteins across different bacterial lineages.
• Understanding these mechanisms can inform strategies targeting essential micronutrient uptake in plant pathogens.