Selective Reactivity of H2S with GlnE7 and HisE7 in Hemoglobins: Implications for Organisms

University Of Puerto Rico Mayaguez, Mayaguez PR

Investigators

Abstract

Organisms that live in sulfide-rich environments harbor symbiotic chemoautotrophic bacteria that, in the presence of oxygen, oxidize sulfide and fix carbon dioxide. The biological molecule responsible for delivering hydrogen sulfide (H2S) and oxygen to these bacteria is the heme protein hemoglobin (Hb). Hb protects these organisms from H2S toxicity and helps maintain their symbiotic relationship with the endosymbiont species. Hemoglobins from these invertebrate organisms show variability in the distal chemical structure and stereochemistry. While cytoplasmic hemoglobins bind and transport their respective ligands via the heme active site, extracellular hemoglobins deliver H2S and O2 simultaneously, delivering H2S using sulfhydryl or organometallic Zn clusters outside the heme chromophore. It is hypothesized that a single amino acid (glutamine or histidine at position E7) is responsible for the difference in H2S toxicity and heme reactivity. The results of this project would provide a deeper understanding of the unique routes for hydrogen sulfide transport and the decreased hydrogen sulfide toxicity in particular organisms. BROADER IMPACTS This interdisciplinary research project will be used as teaching tool to mentor graduate and undergraduate students, as well as to increase their knowledge and communication skills through scientific presentations to pre-college students and teachers via visits to local schools.