Myoglobin at pH 3: Dynamics of myoglobin with the iron-proximal histidine bond broken

Brunori and co-workers have shown that in Mb the proximal histidine (F8) protonates, causing the histidine-iron bond to break with a pK of 3.45. We measured the rebinding kinetics of CO to myoglobin (Mb) at pH3 in 75% glycerol/water in the Soret from 10K to 300K and 50 ns to 100 s. Below about 200K, the observed nonexponential kinetics is attributed to rebinding from the pocket, process I. The resulting distribution of enthalpic barriers for process I peaks at about 1 kJ/mol compared to 10 kJ/mol for Mb at pH7; the pre-exponential for Mb at pH3 is $\sim$10$\sp{11}$ compared to $\sim$10$\sp9$ s$\sp{-1}$ for Mb at pH7. The proximal histidine bond in Mb thus contributes significantly to both the enthalpic and entropic barriers at the heme. The enthalpy distribution does not fit the rebinding data for Mb at pH 3 as well as it does for Mb at pH 7 and neither does an entropy distribution. Slightly better fits were obtained by distributing both the entropic and the enthalpic barriers.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Biophysics

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2011

Author dc:creator

• Cowen, Benjamin Ring

Contributors dc:contributor

• Frauenfelder, Hans

• Biophysics, General

Statement dc:rights

• Copyright 1990 Cowen, Benjamin Ring

Language dc:language

eng

Identifier

AAI9114213
(UMI)AAI9114213

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/23117