Arianna Celis
Arianna Celis

Speaker: Arianna Celis, doctoral student,
Department of Chemistry & Biochemistry,
Montana State University

Date: Friday, March 10, 2017
Time: 3:10 PM
Place: Byker Auditorium, Chemistry & Biochemistry Building
Title: The last stop on a new road to heme: Using protein structure to unravel the reaction mechanism of a novel enzyme in pathogenic Gram-positive bacteria


Known as the “pigments of life,” modified tetrapyrroles such as hemes and chlorophylls are not only beautiful and colorful, but play vital roles in life processes like respiration and photosynthesis. Heme is one of nature’s most ancient and versatile co-factors and is essential for aerobic life. A pathway for how this molecule is synthesized in most gram-positive bacteria, which includes many pathogens such as Staphylococcus aureus, has recently been proposed. This pathway ends in a step catalyzed by an unusual enzyme known as HemQ. The mechanism by which HemQ performs its function is of great interest as some have proposed it to be a potential target for antibiotic treatment against gram-positive bacterial pathogens. Using the HemQ from Staphylococcus aureus, the oxidant that drives this reaction, the oxidation state of the iron at the start of the reaction, and the major intermediates formed during this reaction have been identified. In addition, the first substrate-bound X-ray crystallography structure of HemQ has been obtained. With these results, a mechanism for how this unique enzyme catalyzes its reaction is proposed and will be presented here.

About the speaker

Arianna Celis is the recipient of a 2016 Kopriva Graduate Student Fellowship.