title: Unfolding pathways of human serum albumin: evidence for sequential unfolding and folding of its three domains.
abstract: Human serum albumin (HSA) contains three alpha-helical domains (I-III). The unfolding process of these domains was monitored using covalently bound fluorescence probes; domain I was monitored by N-(1-pyrene)maleimide (PM) conjugated with cys-34, domain II was monitored by the lone tryptophan residue and domain III was followed by p-nitrophenyl anthranilate (NPA) conjugated with Tyrosine-411 (Tyr-411). Using domain-specific probes, we found that guanidium hydrochloride-induced unfolding of HSA occurred sequentially. The unfolding of domain II preceded that of domain I and the unfolding of domain III followed that of domain I. In addition, the domains I and III refolded within the dead time of the fluorescence recovery experiment while the refolding of domain II occurred slowly. The results suggest that individual domain of a multi-domain protein can fold and unfold sequentially.
authors.affiliation: School of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai 400076, India. msantra@iitb.ac.in
authors.forename: Manas Kumar
authors.initials: MK
authors.lastname: Santra
authors.forename: Abhijit
authors.initials: A
authors.lastname: Banerjee
authors.forename: Obaidur
authors.initials: O
authors.lastname: Rahaman
authors.forename: Dulal
authors.initials: D
authors.lastname: Panda
mesh_terms: D002942:Circular Dichroism; D003545:Cysteine / Q000737:chemistry; D005453:Fluorescence; D005456:Fluorescent Dyes / Q000737:chemistry; D006801:Humans; D007700:Kinetics; D008301:Maleimides / Q000737:chemistry; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D012709:Serum Albumin / Q000737:chemistry*; D014364:Tryptophan / Q000737:chemistry; D014443:Tyrosine / Q000737:chemistry; D062367:ortho-Aminobenzoates / Q000737:chemistry
chemical_list: D005456:Fluorescent Dyes; D008301:Maleimides; D012709:Serum Albumin; D062367:ortho-Aminobenzoates; C016616:4-nitrophenyl anthranilate; D014443:Tyrosine; D014364:Tryptophan; C003944:N-(3-pyrene)maleimide; D003545:Cysteine