Wednesday Colloquia

Mechanisms of motor-driven macromolecular machines: insights from nucleotide-dependent restriction enzymes

by Prof. Saikrishnan Kayarat (IISER Pune)

Wednesday, June 16, 2021 from to (Asia/Kolkata)
at Online through ZOOM Webinar ( Zoom link: )
Meeting ID: 979 6325 9354 Pass code: 04072020
A number of cellular activities essential for life are carried out by motor-driven proteinaceous macromolecules that resemble machines. The motor in a macromolecular machine hydrolyzes the cellular energy currency nucleoside triphosphates (often ATP or GTP) and the energy released is harnessed to drive other functions of the macromolecular machine. How motor-driven macromolecular machines function has enthralled and engrossed biologists, chemists and physicists alike. My laboratory has been carrying out biochemical, biophysical and structural studies of nucleotide-dependent restriction enzymes as model systems to understand the mechanism of macromolecular machines. The nucleotide-dependent restriction enzymes are one of the most prominent bacterial defense systems against invading foreign DNA. These enzymes nucleolytically cleave foreign DNA and thus protect the host bacterial cell from viral infection and also control horizontal transfer of DNA, including acquisition of antibiotic resistance genes and pathogenicity islands. To cut the DNA these enzymes require the inbuilt motor to hydrolyze nucleotide. In my talk I will describe our findings on how the motor runs along the DNA track to activate DNA cleavage, while guzzling the energy currency. I will also discuss of ‘energy efficient’ restriction enzymes which hydrolyze fewer nucleotides to achieve a conformational state proficient in long-range diffusion along the DNA track, which activates DNA cleavage. In conclusion, I will discuss how coupling the motor activity to DNA cleavage can make a restriction enzyme a potent molecular shredder.


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Tumuluri, V.S., et al. (2021). Mechanism of DNA cleavage by the endonuclease SauUSI: a major barrier to horizontal gene transfer and antibiotic resistance in Staphylococcus aureus. Nucleic Acids Res., 2021, 49, 2161–2178.