Related Experiment Video
Updated: Jul 22, 2026

Experimental and Imaging Techniques for Examining Fibrin Clot Structures in Normal and Diseased States
Published on: April 1, 2015
Carboxyl-terminal modification alters the subunit interactions and assembly pathways of normal and sickle hemoglobins
1Department of Chemistry, College of Arts and Sciences, University of Massachusetts, Lowell 01854, USA.
Abstract:
Parallel isofocusing studies established that carboxypeptidase A removal of the His-146 (HC3) and Tyr-145 (HC2) residues of beta heme subunits affected the assembly properties of both Des beta(A) and Des beta(S) with alpha heme chains, albeit to differing degrees. Indeed, the rate of Des beta(A) oligomer dissociation (k1), as determined by visible spectroscopy, was 4.3-fold faster than that of its native beta(A) counterpart. Furthermore, Soret spectral studies have affirmed distinct rates of normal (HbA), sickle (HbS), and Des HbA hemoglobin assembly (k'2) from their alpha and beta [Des beta(A)] heme-containing monomers. Matching kinetic analysis of Des beta(A) and Des beta(S) chain assembly (with an identical a chain) revealed 4.6- and 7.8-fold faster combination rates than those seen for beta(A) and beta(S) chains, respectively. This 3-fold disparity in rates strongly supports the critical role of the beta-6 (A3) residue, and its amino-terminal region, in a chain partner recognition and subsequent human hemoglobin assembly.
Related Concept Videos
Multiple Allele Traits
Protein and Protein Structure
A protein's shape is critical to its function. For example, an enzyme can...
Protein Complex Assembly
Many viruses self-assemble into a fully functional unit using the infected host cell to...
Cooperative Allosteric Transitions
Covalently Linked Protein Regulators
These groups modify specific amino acids in a protein.
Protein Modifications in the RER
Broadly, these modifications can be categorized into four main categories — glycosylation, formation of disulfide bonds, assembly of protein subunits, and specific proteolytic cleavages like removal of signal sequences.

