Type: Article

Catalytically impaired TrpA subunit of tryptophan synthase from Chlamydia trachomatis is an allosteric regulator of TrpB

Karolina Michalska, Samantha Wellington, Natalia Maltseva, Robert Jedrzejczak, Nelly Selem?Mojica, L Rodrigo Rosas?Becerra, Francisco Barona?Gómez, Deborah T Hung, Andrzej Joachimiak;

Abstract:

Intracellular growth and pathogenesis of Chlamydia species is controlled by the availability of tryptophan, yet the complete biosynthetic pathway for l?Trp is absent among members of the genus. Some representatives, however, preserve genes encoding tryptophan synthase, TrpAB – a bifunctional enzyme catalyzing the last two steps in l?Trp synthesis. TrpA (subunit ?) converts indole?3?glycerol phosphate into indole and glyceraldehyde?3?phosphate (? reaction). The former compound is subsequently used by TrpB (subunit ?) to produce l?Trp in the presence of l?Ser and a pyridoxal 5??phosphate cofactor (? reaction). Previous studies have indicated that in Chlamydia, TrpA has lost its catalytic activity yet remains associated with TrpB to support the ? reaction. Here, we provide detailed analysis of the TrpAB from C. trachomatis D/UW?3/CX, confirming that accumulation of mutations in the active site of TrpA …