title: Structural and folding dynamic properties of the T70N variant of human lysozyme.
abstract: Definition of the transition mechanism from the native globular protein into fibrillar polymer was greatly improved by the biochemical and biophysical studies carried out on the two amyloidogenic variants of human lysozyme, I56T and D67H. Here we report thermodynamic and kinetic data on folding as well as structural features of a naturally occurring variant of human lysozyme, T70N, which is present in the British population at an allele frequency of 5% and, according to clinical and histopathological data, is not amyloidogenic. This variant is less stable than the wild-type protein by 3.7 kcal/mol, but more stable than the pathological, amyloidogenic variants. Unfolding kinetics in guanidine are six times faster than in the wild-type, but three and twenty times slower than in the amyloidogenic variants. Enzyme catalytic parameters, such as maximal velocity and affinity, are reduced in comparison to the wild-type. The solution structure, determined by 1H NMR and modeling calculations, exhibits a more compact arrangement at the interface between the beta-sheet domain and the subsequent loop on one side and part of the alpha domain on the other side, compared with the wild-type protein. This is the opposite of the conformational variation shown by the amyloidogenic variant D67H, but it accounts for the reduced stability and catalytic performance of T70N.
authors.affiliation: Dipartimento di Scienze e Tecnologie Biomediche, Università di Udine, 33100 Udine, Italy.
authors.forename: Gennaro
authors.initials: G
authors.lastname: Esposito
authors.forename: Julian
authors.initials: J
authors.lastname: Garcia
authors.forename: Palma
authors.initials: P
authors.lastname: Mangione
authors.forename: Sofia
authors.initials: S
authors.lastname: Giorgetti
authors.forename: Alessandra
authors.initials: A
authors.lastname: Corazza
authors.forename: Paolo
authors.initials: P
authors.lastname: Viglino
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Chiti
authors.forename: Alessia
authors.initials: A
authors.lastname: Andreola
authors.forename: Pascal
authors.initials: P
authors.lastname: Dumy
authors.forename: David
authors.initials: D
authors.lastname: Booth
authors.forename: Philip N
authors.initials: PN
authors.lastname: Hawkins
authors.forename: Vittorio
authors.initials: V
authors.lastname: Bellotti
mesh_terms: D000483:Alleles; D000682:Amyloid / Q000737:chemistry; D000686:Amyloidosis / Q000378:metabolism; D002384:Catalysis; D002942:Circular Dichroism; D018360:Crystallography, X-Ray; D004305:Dose-Response Relationship, Drug; D005838:Genotype; D019791:Guanidine / Q000737:chemistry; D006801:Humans; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D009113:Muramidase / Q000737:chemistry*; D011487:Protein Conformation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D013696:Temperature; D013816:Thermodynamics; D013997:Time Factors; D014466:Ultraviolet Rays
chemical_list: D000682:Amyloid; D009113:Muramidase; D019791:Guanidine