Past Event: Oden Institute Seminar

Globin Gates and Tunnels: Different Ways to Capture O2 and Detoxify NO

John S. Olson, Ralph and Dorothy Looney Professor, Ralph and Dorothy Looney Professor, Rice University

Abstract

Over the past ten years, large numbers of hemoglobin genes have been discovered and appear in all kingdoms of life, from prokaryotes to both higher plants and animals. Even though the overall protein fold and heme binding pocket are conserved in thse globins, the mechanisms for O2 binding and stabilization do differ, in some cases dramatically. The major pathway for O2 binding to vertebrate myoglobins and hemoglobins involves transient upward movement of the distal histidine , allowing ligand capture in the distal pocket and binding to the iron atom. In contrast, the mini-globin from the sea worm Cerebratulus lacteus and certain truncated bacterial hemoglobns has an alternative pathway involving an apolar tunnel through the globin interior between the E and H helices that is made accessible by loss of the N-terminal A helix. These results demonstrate that there is more than one way for apolar diatomic gases to enter proteins and "find" metal centers. *Refreshments served at 3:00