Decoding allosteric communication pathways in protein lysine acetyltransferase.

Area of Science:

• Biochemistry
• Molecular Biology
• Structural Biology

Background:

• Protein lysine acetylation regulates essential bacterial processes, including metabolism.
• Cyclic adenosine monophosphate (cAMP) influences protein lysine acetyltransferase (PAT) activity and transcription in E. coli.
• Mycobacterium tuberculosis PatA (Mt-PatA) exists in both activated and autoinhibited states, with the cAMP activation mechanism unclear.

Purpose of the Study:

• To elucidate the mechanism of cAMP-mediated allosteric activation of Mt-PatA.
• To understand how cAMP binding transmits signals over a distance to the catalytic site.
• To identify key structural rearrangements involved in relieving Mt-PatA autoinhibition.

Main Methods:

• All-atom molecular dynamics (MD) simulations were extensively performed.
• A residue-residue dynamic correlation network was constructed.
• Site-directed mutagenesis (His173 to Lys) was employed.

Main Results:

• cAMP binds to the regulatory domain, 32 Å from the catalytic site, inducing conformational changes.
• A ~40° rotation of the regulatory domain around Ser144 relieves autoinhibition by moving a 'molecular Lid'.
• The molecular Lid refolds, creating an activator binding site, and a His173 mutation suggests direct acetylation involvement.

Conclusions:

• A detailed allosteric framework for Mt-PatA activation by cAMP has been established.
• The study reveals intermediate states crucial for long-distance signal transmission in bacterial regulation.
• The findings provide insights into the regulation of protein acetylation in M. tuberculosis.