Phosphorylation of Staphylococcus aureus Protein-Tyrosine Kinase Affects the Function of Glucokinase and Biofilm Formation.
When Staphylococcus aureus is grown in the presence of high concentration of external glucose, this sugar is phosphorylated by glucokinase (glkA) to form glucose-6-phosphate. This product subsequently enters into anabolic phase, which favors biofilm formation. The presence of ROK (repressor protein, open reading frame, sugar kinase) motif, phosphate-1 and -2 sites, and tyrosine kinase sites in glkA of S. aureus indicates that phosphorylation must regulate the glkA activity. The aim of the present study was to identify the effect of phosphorylation on the function of S. aureus glkA and biofilm formation.



Pure glkA and protein-tyrosine kinase (BYK) of S. aureus ATCC 12600 were obtained by fractionating the cytosolic fractions of glkA1 and BYK-1 expressing recombinant clones through nickel metal chelate column. The pure glkA was used as a substrate for BYK and the phosphorylation of glkA was confirmed by treating with reagent A and resolving in SDS-PAGE, as well as staining with reagent A. The kinetic parameters of glkA and phosphorylated glkA were determined spectrophotometrically, and in silico tools were used for validation. S. aureus was grown in brain heart infusion broth, which was supplemented with glucose, and then biofilm units were calculated.



Fourfold elevated glkA activity was observed upon the phosphorylation by BYK. Protein-protein docking analysis revealed that glkA structure docked close to the adenosine triphosphate-binding site of BYK structure corroborating the kinetic results. Further, S. aureus grown in the presence of elevated glucose concentration exhibited an increase in the rate of biofilm formation.



The elevated function of glkA is an essential requirement for increased biofilm units in S. aureus, a key pathogenic factor that helps its survival and spread the infection.
Department of Biotechnology, Sri Venkateswara Institute of Medical Sciences, Tirupati 517 507, Andhra Pradesh, India.
Dudipeta
D
Vasu
Department of Biotechnology, Sri Venkateswara Institute of Medical Sciences, Tirupati 517 507, Andhra Pradesh, India.
Pasupuleti Santhosh
PS
Kumar
Department of Biotechnology, Sri Venkateswara Institute of Medical Sciences, Tirupati 517 507, Andhra Pradesh, India.
Uppu Venkateswara
UV
Prasad
Department of Biotechnology, Sri Venkateswara Institute of Medical Sciences, Tirupati 517 507, Andhra Pradesh, India.
Vimjam
V
Swarupa
Department of Biotechnology, Sri Venkateswara Institute of Medical Sciences, Tirupati 517 507, Andhra Pradesh, India.
Sthanikam
S
Yeswanth
Department of Biotechnology, Sri Venkateswara Institute of Medical Sciences, Tirupati 517 507, Andhra Pradesh, India.
Lokanathan
L
Srikanth
Department of Biotechnology, Sri Venkateswara Institute of Medical Sciences, Tirupati 517 507, Andhra Pradesh, India.
Manne Mudhu
MM
Sunitha
Department of Microbiology, Sri Venkateswara Institute of Medical Sciences, Tirupati 517 507, Andhra Pradesh, India.
Abhijith
A
Choudhary
Department of Biotechnology, Sri Venkateswara Institute of Medical Sciences, Tirupati 517 507, Andhra Pradesh, India.
Potukuchi Venkata Gurunadha Krishna
PV
Sarma
Glucokinase; Protein-tyrosine kinase; in silico analysis
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