ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Interacts with GarA in vitro. When artificially expressed from expression vectors, encodes an active kinase, which is able to block the lysosomal delivery of mycobacteria inside macrophages. However, while PknG transcripts are found in M.smegmatis, expression of PknG is blocked on a translational level in this non-pathogenic species. This lack of efficient translation is caused by regulatory elements in the upstream region of the gene (PubMed:19210624). Belongs to the protein kinase superfamily. Ser/Thr protein kinase family.