ThrH, a homoserine kinase isozyme with in vivo phosphoserine phosphatase activity in Pseudomonas aeruginosa

A novel gene called thrH encodes a protein with an in vivo homoserine-kinase-like activity in Pseudomonas aeruginosa when expressed in Escherichia coli thrB mutant strains. Threonine auxotrophy is observed only in Pseudomonas aeruginosa when both thrB and thrH are simultaneously activated. Overexpression of the new gene also allows complementation of serine auxotrophy of Escherichia coli and Pseudomonas aeruginosa serB strains. In addition, sequence homology is observed between thrH and the serB proteins from different organisms.