Bacterial genomics have revealed the widespread occurrence of eukaryotic-like protein kinases in prokaryotes, but little is known about their regulation, endogenous substrates, and physiological role. The present study concerns one of these enzymes, the serine/threonine protein kinase PknF from Mycobacterium tuberculosis. It is shown that, in addition to its autokinase activity, PknF is able to phosphorylate Rv1747, a newly described ABC transporter. This reaction appears to involve two FHA domains of Rv1747. It is suggested that recruitment and phosphorylation of Rv1747 depend on the interaction between its two non-redundant FHA domains and the autophosphorylated form of PknF.