Specificity and Reactivity of Mycobacterium tuberculosis Serine/Threonine Kinases PknG and PknB

Abstract

Mycobacterium tuberculosis (Mtb), the causative agent of Tuberculosis, has 11 eukaryotic-like serine/threonine protein kinases, which play essential roles in cell growth, signal transduction, and pathogenesis. Protein kinase G (PknG) regulates the carbon and nitrogen metabolism by phosphorylation of the glycogen accumulation regulator (GarA) protein at Thr21. Protein kinase B (PknB) is involved in cell wall synthesis and cell shape, as well as phosphorylates GarA but at Thr22. While PknG seems to be constitutively activated and recognition of GarA requires phosphorylation in its unstructured tail, PknB activation is triggered by phosphorylation of its activation loop, which allows binding of the forkhead-associated domain of GarA. In the present work, we used molecular dynamics and quantum-mechanics/ molecular mechanics simulations of the catalytically competent complex and kinase activity assays to understand PknG/PknB specificity and reactivity toward GarA. Two hydrophobic residues in GarA, Val24 and Phe25, seem essential for PknG binding and allow specificity for Thr21 phosphorylation. On the other hand, phosphorylated residues in PknB bind Arg26 in GarA and regulate its specificity for Thr22. We also provide a detailed analysis of the free energy profile for the phospho-transfer reaction and show why PknG has a constitutively active conformation not requiring priming phosphorylation in contrast to PknB. Our results provide new insights into these two key enzymes relevant for Mtb and the mechanisms of serine/threonine phosphorylation in bacteria.

Identification of Interacting Proteins of Transcription Factor DpAP2 Related to Carotenoid Biosynthesis From Marine Microalga Dunaliella parva

“…The serine/threonine kinase Akt is a key factor regulating glucose and lipid energy metabolism, which is activated in response to various stimuli such as cell stress and various hormones and drugs (Miao et al, 2022). The eukaryotic-like serine/threonine protein kinases play important roles in cell growth and signal transduction in Mycobacterium tuberculosis (Burastero et al, 2022). Protein kinase G regulates the carbon and nitrogen metabolism by the phosphorylation of the glycogen accumulation regulator (GarA) at Thr21 (Burastero et al, 2022).…”

“…The eukaryotic-like serine/threonine protein kinases play important roles in cell growth and signal transduction in Mycobacterium tuberculosis (Burastero et al, 2022). Protein kinase G regulates the carbon and nitrogen metabolism by the phosphorylation of the glycogen accumulation regulator (GarA) at Thr21 (Burastero et al, 2022). Protein kinase B is related to the formation of the cell shape, cell wall synthesis, and phosphorylation of GarA at Thr22 (Burastero et al, 2022).…”

“…Protein kinase G regulates the carbon and nitrogen metabolism by the phosphorylation of the glycogen accumulation regulator (GarA) at Thr21 (Burastero et al, 2022). Protein kinase B is related to the formation of the cell shape, cell wall synthesis, and phosphorylation of GarA at Thr22 (Burastero et al, 2022). In a word, protein serine/ threonine kinase plays an important role in cell metabolism.…”