Crystal structure of GDP-mannose dehydrogenase:: A key enzyme of alginate biosynthesis in P-aeruginosa

The enzyme GMD from Pseudomonas aeruginosa catalyzes the committed step in the synthesis of the exopolysaccharide alginate. Alginate is a major component of P. aeruginosa biofilms that protect the bacteria from the host immune response and antibiotic therapy. The 1.55 Angstrom crystal structure of GMD in ternary complex with its cofactor NAD(H) and product GDP-mannuronic acid reveals that the enzyme forms a domain-swapped dimer with two polypeptide chains contributing to each active site. The extensive dimer interface provides multiple opportunities for intersubunit communication. Comparison of the GMD structure with that of UDP-glucose dehydrogenase reveals the structural basis of sugar binding specificity that distinguishes these two related enzyme families. The high-resolution structure of GMD provides detailed information on the active site of the enzyme and a template for structure-based inhibitor design.