Katarina Sirka


Faculty Mentor: JoAnne Stubbe

Direct Supervisor: Kanchana Ravichandran

Home University: Colby College

Major: Chemistry



I was born and raised in Serbia. I attended last two years of high school in United World College in Canada where I completed International Baccalaureate and received a scholarship to study in the United States. I am currently a senior at Colby College in Maine. I am majoring in chemistry with a concentration in biochemistry and cell and molecular biology, and minoring in mathematics and Russian language and literature. My goal is to pursue a Ph.D. in Biochemistry, and eventually become involved in medical research. In my free time I enjoy reading, swimming, playing volleyball, traveling, and spending time with my friends.


Role of E52 in proton-coupled electron transfer in the Escherichia coli ribonucleotide reductase β2 subunit

Ribonucleotide reductase (RNR) catalyzes the conversion of ribonucleotides to their corresponding deoxyribonucleotides which are in turn used in DNA synthesis and repair in all organisms. The central role of RNR in cell growth has made it an important target for anticancer and antivirus treatments; therefore, understanding the molecular mechanism that underlies RNR’s function is essential for further investigation of its therapeutic potential. The mechanism for the radical-based catalytic activity of RNR is proton-coupled electron transfer (PCET) which is not fully known, since radical propagation and chemistry occur too fast to be observed. In order to study this mechanism, E52 amino acid proposed to play an essential role in PCET was altered in NrdB protein and its effects were examined by mean of spectrophotometric assays. The results showed that when E52 is changed to alanine the enzyme loses its activity, and when E52 is changed to aspartic acid it becomes insoluble.