Control of Ligand Binding to Heme Proteins: The Role of The Distal Histidine

We have investigated the effect of the distal histidine on the recombination rates of CO and O(,2) to sperm whale myoglobin, separated beta chains of normal human hemoglobin and to the beta chains of hemoglobin Zurich. The recombination was measured using flash photolysis from 300 to 40 K, on a time scale of 100 ns to 300 s. Lowering the pH of the solution from 7.0 to 5.0, we find a 3 kJ/mol and 1.5 kJ/mol decrease in the final barrier for CO binding to myoglobin and the separated chains of human hemoglobin, respectively. The distal histidine, His E 7, is identified as the titratable group by observing no pH dependence in the rates when CO binds to the beta chains of hemoglobin Zurich, a mutant of hemoglobin lacking a distal histidine in the beta chains. We postulate a charge-dipole interaction between the CO and the protonated histidine, since the recombination of the symmetric ligand, O(,2), is pH independent.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Physics

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2015

Author dc:creator

• Reinisch, Lou

• Physics, General

Language dc:language

eng

Identifier

(UMI)AAI8218546

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/77348