Biochemistry, Department of


First Advisor

Mark A. Wilson

Second Advisor

Donald Becker

Third Advisor

David Berkowitz

Date of this Version

Spring 4-15-2020


A DISSERTATION Presented to the Faculty of The Graduate College at the University of Nebraska In partial Fulfillment of Requirements For the Degree of Doctor of Philosophy, Major: Biochemistry, Under the Supervision of Professor Mark A. Wilson. Lincoln, Nebraska: May 2020

Copyright 2020 Medhanjali Dasgupta


Post-translational modification of cysteine residues can regulate protein function and is essential for catalysis by cysteine-dependent enzymes. Covalent modifications neutralize charge on the reactive cysteine thiolate anion and thus alter the active site electrostatic environment. Although a vast number of enzymes rely on cysteine modification for function, precisely how altered structural and electrostatic states of cysteine affect protein dynamics, which in turn, affects catalysis, remains poorly understood.

Here we use X-ray crystallography, computer simulations, site directed mutagenesis and enzyme kinetics to characterize how covalent modification of the active site cysteine residue in the enzyme, isocyanide hydratase (ICH), affects the protein conformational ensemble during catalysis. Our results suggest that cysteine modification may be a common and likely underreported means for regulating protein conformational dynamics. This thesis will also include ongoing work with ICH homologs, showing that Cys covalent modification-gated helical dynamics in Cys dependent enzymes is common to enzymes of this family.

Advisor: Dr. Mark. A. Wilson