title: Oligomerization of Sulfolobus solfataricus signature amidase is promoted by acidic pH and high temperature.
abstract: The recombinant amidase from the hyperthermophylic archaeon Sulfolobus solfataricus (SSAM) a signature amidase, was cloned, purified and characterized. The enzyme is active on a large number of aliphatic and aromatic amides over the temperature range 60-95 degrees C and at pH values between 4.0 and 9.5, with an optimum at pH 5.0. The recombinant enzyme is in the form of a dimer of about 110 kD that reversibly associates into an octamer in a pH-dependent reaction. The pH dependence of the state of association was studied using gel permeation chromatography, analytical ultracentrifugation and dynamic light scattering techniques. At pH 7.0 all three techniques show the presence of two species, in about equal amounts, which is compatible with the existence of a dimeric and an octameric form. In decreasing pH, the dimers formed the octameric species and in increasing pH, the octameric species was converted to dimers. Above pH 8.0, only dimers were present, below pH 3.0 only octamers were present. The association of dimers into octamers decreased in non-polar solvents and increased with temperature. A mutant (Y41C) was obtained that did not show this behavior.
authors.affiliation: Dipartimento di Scienze Biochimiche A. Rossi-Fanelli, Università La Sapienza, P.le A. Moro 5, 00185 Roma, Italy.
authors.forename: Anna
authors.initials: A
authors.lastname: Scotto D'Abusco
authors.forename: Rita
authors.initials: R
authors.lastname: Casadio
authors.forename: Gianluca
authors.initials: G
authors.lastname: Tasco
authors.forename: Laura
authors.initials: L
authors.lastname: Giangiacomo
authors.forename: Anna
authors.initials: A
authors.lastname: Giartosio
authors.forename: Valentina
authors.initials: V
authors.lastname: Calamia
authors.forename: Stefania
authors.initials: S
authors.lastname: Di Marco
authors.forename: Roberta
authors.initials: R
authors.lastname: Chiaraluce
authors.forename: Valerio
authors.initials: V
authors.lastname: Consalvi
authors.forename: Roberto
authors.initials: R
authors.lastname: Scandurra
authors.forename: Laura
authors.initials: L
authors.lastname: Politi
mesh_terms: D000577:Amides / Q000378:metabolism; D000581:Amidohydrolases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D019843:Archaeal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008958:Models, Molecular; D008969:Molecular Sequence Data; D008970:Molecular Weight; D011994:Recombinant Proteins / Q000096:biosynthesis; D016415:Sequence Alignment; D013379:Substrate Specificity; D048229:Sulfolobus solfataricus / Q000201:enzymology* / Q000235:genetics; D013696:Temperature
chemical_list: D000577:Amides; D019843:Archaeal Proteins; D011994:Recombinant Proteins; D000581:Amidohydrolases; C019665:amidase