Reversible two-step unfolding of heme–human serum albumin: a 1H-NMR relaxometric and circular dichroism study

Abstract

Human serum albumin (HSA) participates in heme scavenging, the bound heme turning out to be a reactivity center and a powerful spectroscopic probe. Here, the reversible unfolding of heme-HSA has been investigated by 1 H-NMR relaxometry, circular dichroism, and absorption spectroscopy. In the presence of 6 equiv of myristate (thus fully saturating all available fatty acid binding sites in serum heme-albumin), 1.0 M guanidinium chloride induces some unfolding of heme-HSA, leading to the formation of a folding intermediate; this species is characterized by increased relaxivity and enhanced dichroism signal in the Soret region, suggesting a more compact heme pocket conformation. Heme binds to the folding intermediate with

Evidence for pH-dependent multiple conformers in iron(II) heme–human serum albumin: spectroscopic and kinetic investigation of carbon monoxide binding

“…Furthermore, this behavior, which underlies the occurrence of multiple conformations of iron(II) heme-HSA, may have great impact on the function of heme-HSA as a metabolite and drug transporter, since this proton-linked modulation is reflected in its capability of interacting with molecules circulating in the bloodstream, as previously demonstrated [3,8,20,22,[29][30][31][32]. Therefore, HSA, not only acting as a heme carrier but also displaying transient heme-based properties, represents a case for ''chronosteric effects'' [62], which opens the scenario toward the possibility of a time-and metabolite-dependent multiplicity of roles for HSA.…”

“…At pH [ 8.0 and in the absence of ligands, HSA exhibits the basic form, which is characterized by a high affinity for some ligands (e.g., heme). Ligands that bind with the highest affinity to one of the conformational states may allosterically modulate the HSA transition [3,8,20,22,[29][30][31][32].…”

Allostery in a monomeric protein: The case of human serum albumin

“…Crystallographic and solution evidences indicate that the observed conformational transition is not determined by the highest affinity binding events, rather it cooperatively takes place when the protein is half-saturated. Noteworthy, two medium-affinity sites (i.e., FA2 and FA3) are located at domain interfaces and therefore may drive the conformational transition observed upon FAs binding [21][22][23][24]32,51,78].…”

Influences of cationic, anionic, and nonionic surfactants on alkaline-induced intermediate of bovine serum albumin

“…The mechanism by which such an intricate process takes place still eludes protein chemists and molecular biologists. To understand the factors governing the formation of three-dimensional structures of proteins, it is important to elucidate the hierarchy of interactions that stabilize native conformation and partially folded intermediate [1][2][3][4][5]. Solvent perturbation study is a good approach to evaluate the stabilizing force of protein structure since alcohol, polyols and sugars, etc.…”