A eukaryotic-type protein kinase, SpkA, is required for normal motility ofthe unicellular cyanobacterium Synechocystis sp strain PCC 6803

The genome of the unicellular cyanobacterium Synechocystis sp, strain PCC 6 803 comprises many open reading frames (ORFs) which putatively encode eukar yotic-type protein kinase and protein phosphatase. Based on gene disruption analysis, a region of the hypothetical ORF sll1575, which retained a part of the protein kinase motif, was found to be required for normal motility i n the original isolate of strain PCC 6803, Sequence determination revealed that in this strain sll1575 was part of a gene (designated spkA) which harb ored an entire eukaryotic-type Ser/Thr protein kinase motif, Strain ATCC 27 184 and a glucose-tolerant strain derived from the same isolate as the PCC strain had a frameshift mutation dividing spkA into ORFs sll1574 and sll157 5, The structural integrity of spkA agreed well with the motility phenotype , determined by colony morphology on agar plates. The spkA gene was express ed in Escherichia coli as a His-tagged protein, which was purified by Ni2affinity chromatography. With [gamma-P-32]ATP, SpkA was autophosphorylated and transferred the phosphate group to casein, myelin basic protein, and hi stone, SpkA also phosphorylated several proteins in the membrane fraction o f Synechocystis cells, These results suggest that SpkA is a eukaryotic-type Ser/Thr protein kinase and regulates cellular motility via phosphorylation of the membrane proteins in Synechocystis.