title: Conformational transitions of the three recombinant domains of human serum albumin depending on pH.
abstract: Human serum albumin (HSA) is a protein of 66.5 kDa that is composed of three homologous domains, each of which displays specific structural and functional characteristics. HSA is known to undergo different pH-dependent structural transitions, the N-F and F-E transitions in the acid pH region and the N-B transition at slightly alkaline pH. In order to elucidate the structural behavior of the recombinant HSA domains as stand-alone proteins and to investigate the molecular and structural origins of the pH-induced conformational changes of the intact molecule, we have employed fluorescence and circular dichroic methods. Here we provide evidence that the loosening of the HSA structure in the N-F transition takes place primarily in HSA-DOM III and that HSA-DOM I undergoes a structural rearrangement with only minor changes in secondary structure, whereas HSA-DOM II transforms to a molten globule-like state as the pH is reduced. In the pH region of the N-B transition of HSA, HSA-DOM I and HSA-DOM II experience a tertiary structural isomerization, whereas with HSA-DOM III no alterations in tertiary structure are observed, as judged from near-UV CD and fluorescence measurements.
authors.affiliation: Institute of Applied Microbiology, University of Agricultural Sciences, Muthgasse 18, A-1190 Vienna, Austria.
authors.forename: M
authors.initials: M
authors.lastname: Dockal
authors.forename: D C
authors.initials: DC
authors.lastname: Carter
authors.forename: F
authors.initials: F
authors.lastname: Rüker
mesh_terms: D006801:Humans; D006863:Hydrogen-Ion Concentration; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics; D012709:Serum Albumin / Q000737:chemistry* / Q000235:genetics
chemical_list: D011994:Recombinant Proteins; D012709:Serum Albumin