Signal transmission between subunits in the hemoglobin T-state

• Published in: Journal of molecular biology Vol. 284; no. 5; pp. 1707 - 1716
• Main Authors: Englander, J J, Rumbley, J N, Englander, S W
• Format: Journal Article
• Language: English
• Published: England 18-12-1998
• Subjects: Cyanides - chemistry; Heme - chemistry; Hemoglobins - chemistry; Hemoglobins - genetics; Hemoglobins - metabolism; Humans; Hydrogen; Protein Conformation; Recombinant Proteins - chemistry; Recombinant Proteins - genetics; Recombinant Proteins - metabolism; Signal Transduction - physiology
• ISSN: 0022-2836
• DOI: 10.1006/jmbi.1998.2279

To study allosteric mechanism in hemoglobin, a hydrogen-exchange method was used to measure ligand-dependent changes in structural free energy at defined allosterically sensitive positions. When the two alpha-subunits are CN-met liganded, effects can be measured locally, within the alpha-subunit, and also remotely, within the beta-subunit, even though the quaternary structure remains in the T conformation. When the two beta-subunits are liganded, effects occur at the same positions. The effects seen are the same, independently of whether ligands occupy the alpha-chain hemes or the beta-chain hemes. Control experiments rule out modes of energy transfer other than programmed cross-subunit interaction within the T-state. Cross-subunit transfer may depend on pulling the heme trigger (moving the heme iron into the heme plane) rather than on liganding alone.