title: Probing the stability of native and activated forms of alpha2-macroglobulin.
abstract: alpha2-Macroglobulin (alpha2M) is a 718 kDa homotetrameric proteinase inhibitor which undergoes a large conformational change upon activation. This conformational change can occur either by proteolytic attack on an approximately 40 amino acid stretch, the bait region, which results in the rupture of the four thioester bonds in alpha2M, or by direct nucleophilic attack on these thioesters by primary amines. Amine activation circumvents both bait region cleavage and protein incorporation, which occurs by proteolytic activation. These different activation methods allow for examination of the roles bait region cleavage and thioester rupture play in alpha2M stability. Differential scanning calorimetry and urea gel electrophoresis demonstrate that both bait region cleavage and covalent incorporation of protein ligands in the thioester pocket play critical roles in the stability of alpha2M complexes.
authors.affiliation: Department of Pathology, Duke University Medical Center, Box 3712, Durham, NC 27710, USA.
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Kaczowka
authors.forename: Lara S
authors.initials: LS
authors.lastname: Madding
authors.forename: Kevin L
authors.initials: KL
authors.lastname: Epting
authors.forename: Robert M
authors.initials: RM
authors.lastname: Kelly
authors.forename: George J
authors.initials: GJ
authors.lastname: Cianciolo
authors.forename: Salvatore V
authors.initials: SV
authors.lastname: Pizzo
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D006358:Hot Temperature; D006801:Humans; D008024:Ligands; D008969:Molecular Sequence Data; D010447:Peptide Hydrolases / Q000737:chemistry; D011487:Protein Conformation; D044366:Transition Temperature; D000511:alpha-Macroglobulins / Q000737:chemistry*
chemical_list: D008024:Ligands; D000511:alpha-Macroglobulins; D010447:Peptide Hydrolases