A 4.2-kb SphI-BamHI fragment of chromosomal DNA from Streptomyces granaticolor was cloned and shown to encode a protein with significant sequence similarity to the eukaryotic protein serine/threonine kinases. It consists of 701 amino acids and in the N-terminal part contains all conserved catalytic domains of protein kinases. The C-terminal domain of Pkg2 contains seven tandem repeats of 11 or 12 amino acids with similarity to the tryptophan-docking motif known to stabilize a symmetrical three-dimensional structure called a propeller structure. The pkg2 gene was overexpressed in Escherichia coli, and the gene product (Pkg2) has been found to be autophosphorylated at serine and threonine residues.

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The serine/threonine kinase of S. aureus contains a transmembrane sequence of a length to indicate a single membrane-spanning helix, between cytosolic and extracellular domains, according to this paper. Therefore, it must be an integral membrane protein.

Article Structural Analysis of Staphylococcus aureus Serine/Threonin...