Pyroglutamination-Induced Changes in the Physicochemical Features of a CXCR4 Chemokine Peptide: Kinetic and Structural Analysis

We investigate the physicochemical effects of pyroglutaminationon the QHALTSV-NH2 peptide, a segment of cytosolic helix8 of the human C-X-C chemokine G-protein-coupled receptortype 4 (CXCR4). This modification, resulting from the spontaneousconversion of glutamine to pyroglutamic acid, has significant impactson the physicochemical features of peptides. Using a static approach,we compared the transformation in different conditions and experimentallyfound that the rate of product formation increases with temperature,underscoring the need for caution during laboratory experiments toprevent glutamine cyclization. Circular dichroism experiments revealedthat the QHALTSV-NH2 segment plays a minor role in thestructuration of H8 CXCR4; however, its pyroglutaminated analogueinteracts differently with its chemical environment, showing increasedsusceptibility to solvent variations compared to the native form.The pyroglutaminated analogue exhibits altered behavior when interactingwith lipid models, suggesting a significant impact on its interactionwith cell membranes. A unique combination of atomic force microscopyand infrared nanospectroscopy revealed that pyroglutamination affectssupramolecular self-assembly, leading to highly packed molecular arrangementsand a crystalline structure. Moreover, the presence of pyroglumaticacid has been found to favor the formation of amyloidogenic aggregates.Our findings emphasize the importance of considering pyroglutaminationin peptide synthesis and proteomics and its potential significancein amyloidosis.