Abstract
Kinetics of CO binding to human hemoglobin (Hb) has been followed below neutrality. With respect to the behavior observed at pH 7.0, CO binding to deoxy-Hb at pH 2.3 displays a much faster second-order combination rate constant (1.2 x 10(-7) M-1 s-1) and loss of the autocatalytic character of the kinetic progress curve. The spectroscopic features of the transient deoxy-Hb at pH 2.75 indicate the phenomenon to be related to the cleavage of the proximal histidine N epsilon-Fe bond, as reported for monomeric hemoproteins (Coletta, M., Ascenzi, P., Traylor, T. G., and Brunori, M. (1985) J. Biol. Chem. 260, 4151-4155). The faster CO binding rate constant, higher than that characteristic of the R state, cannot be attributed to either (i) an enhanced dimerization of deoxy-Hb at low pH, or (ii) a quaternary switch of the unliganded form to the R0 state. The data indicate that interaction(s) of the heme on the proximal side is crucial in accounting for the difference in the CO binding rate constant between the two quaternary conformations of hemoglobin.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
