Allosteric Sensing of Fatty Acid Binding by NMR: Application to Human Serum Albumin

Human serum albumin
(HSA) serves not only as a physiological oncotic
pressure regulator and a ligand carrier but also as a biomarker for
pathologies ranging from ischemia to diabetes. Moreover, HSA is a
biopharmaceutical with a growing repertoire of putative clinical applications
from hypovolemia to Alzheimer’s disease. A key determinant
of the physiological, diagnostic, and therapeutic functions of HSA
is the amount of long chain fatty acids (LCFAs) bound to HSA. Here,
we propose to utilize 13C-oleic acid for the NMR-based
assessment of albumin-bound LCFA concentration (CONFA). 13C-Oleic acid primes HSA for a LCFA-dependent allosteric transition
that modulates the frequency separation between the two main 13C NMR peaks of HSA-bound oleic acid (ΔνAB). On the basis of ΔνAB, the overall [12C-LCFA]Tot/[HSA]Tot ratio is reproducibly
estimated in a manner that is only minimally sensitive to glycation,
albumin concentration, or redox potential, unlike other methods to
quantify HSA-bound LCFAs such as the albumin–cobalt binding
assay.