Biological & Soft Matter Seminar: Enzymatic catalysis - lessons from single molecules

Abstract: 

The catalytic mechanisms of complex enzymes may involve a combination of chemical steps and conformational transitions. The latter are oftentimes hidden to traditional biochemical investigations. In the first part of this lecture I will show that single-molecule FRET (smFRET) can be used not only to observe conformational dynamics but also to constrain mechanistic models. This is done by studying QSOX, a catalyst of disulfide bond formation with two active sites.

Both static and dynamic disorder have been found in enzyme molecules. An attempt to understand this phenomenon has led us to the discovery that the well-known enzyme horseradish peroxidase can be inhibited by its product molecules, and that the rate of this inhibition reaction is strongly correlated with the catalytic rate of the enzyme, even in the face of strong disorder. In the second part of the talk I will discuss these results and their surprising implications.

1. Grossman I, Aviram H, Armony G, Horotivz A, Hofmann H, Haran G & Fass D (2015) Single-molecule spectroscopy exposes hidden states in an enzymatic electron relay. Nature Communications 6:8624.

2. Piwonski HM, Goomanovsky M, Bensimon D, Horovitz A, & Haran G (2012) Allosteric inhibition of individual enzyme molecules trapped in lipid vesicles. Proc Natl Acad Sci U S A 109(22):E1437-1443.

Seminar Organizer: Guy Yaacoby