Conservative tryptophan mutants of the protein tyrosine phosphatase YopH exhibit impaired WPD-loop function and crystallize with divanadate esters in their active sites.
Moise G, Gallup NM, Alexandrova AN, Hengge AC, Johnson SJ. Conservative tryptophan mutants of the protein tyrosine phosphatase YopH exhibit impaired WPD-loop function and crystallize with divanadate esters in their active sites. Biochemistry. 2015 Oct 27; 54(42):6490-500.