The Reaction of Cyanate with the a and b Subunits in Hemoglobin
Year: 1973
Type: article
Abstract: To evaluate the influence of oxygenation on the reactivity of hemoglobin to cyanate, oxy- and deoxyhemoglobin were carbamylatedwith a low (2.5 mM) concentration of [14C]-cyanate for up to 100 min. The radioactivity of the isolated tryptic peptides of purified carbamylated globin chains (αc and βc) was determined. Under these reaction conditions, 97% or more of the cyanate was bound to the NH2-terminal peptides of the α and β chains in oxy- as well as in deoxyhemoglobin. A modification of the ρ-chloromercuribenzoate method for chain separation was used to measure the rate of the reaction with cyanate of both types of chians in tetrameric hemoglobin. The reaction of hemoglobin with cyanate was strongly oxygen linked. the α chains were carbamylated twice as rapidly in deoxy- as compared to oxyhemoglobin in both phosphate and bis-tris buffers. The β chain carbamylation was less dependent upon oxygenation of hemoglobin in bis-tris buffer, and did not vary at all with oxygenation in phosphate buffer. Organic Polyphosphates (2,3-diphosphoglycerate and inositol hexaphosphate) inhibited β chain carbamylation selectively. The effect of pH on the carbamylation of α and β chains in deoxyhemoglobin was studied. At a fixed pH, CO2 decreased the reaction rate of α and β chain NH2 termini to the same extent.
Source: Journal of Biological Chemistry
Institution: Harvard University
Language: English
Subfield: Cell Biology
Domain: Life Sciences
Open Access status: hybrid
Estimated APC paid: $3,430
OpenAlex ID: W150843002