title: Heme binding inhibits the fibrillization of amyloidogenic apomyoglobin and determines lack of aggregate cytotoxicity.
abstract: Myoglobin is an alpha-helical globular protein containing two highly conserved tryptophanyl residues at positions 7 and 14 in the N-terminal region. The double W/F replacement renders apomyoglobin highly susceptible to aggregation and amyloid-like fibril formation under physiological conditions. In this work we analyze the early stage of W7FW14F apomyoglobin aggregation following the time dependence of the process by far-UV CD, Fourier-transform infrared (FTIR) spectroscopy, and heme-binding properties. The results show that the aggregation of W7FW14F apomyoglobin starts from a native-like globin state able to bind the prosthetic group with spectroscopic properties similar to those observed for wild-type apoprotein. Nevertheless, it rapidly aggregates, forming amyloid fibrils. However, when the prosthetic group is added before the beginning of aggregation, amyloid fibrillization is inhibited, although the aggregation process is not prevented. Moreover, the apomyoglobin aggregates formed in these conditions are not cytotoxic differently from what is observed for all amyloidogenic proteins. These results open new insights into the relationship between the structure adopted by the protein into the aggregates and their ability to trigger the impairment of cell viability.
authors.affiliation: Dipartimento di Biochimica e Biofisica, Seconda Università degli Studi di Napoli, Via L. De Crecchio 7, 80138 Napoli, Italy.
authors.forename: Clara
authors.initials: C
authors.lastname: Iannuzzi
authors.forename: Silvia
authors.initials: S
authors.lastname: Vilasi
authors.forename: Marianna
authors.initials: M
authors.lastname: Portaccio
authors.forename: Gaetano
authors.initials: G
authors.lastname: Irace
authors.forename: Ivana
authors.initials: I
authors.lastname: Sirangelo
mesh_terms: D000682:Amyloid / Q000737:chemistry* / Q000378:metabolism; D000818:Animals; D001059:Apoproteins / Q000737:chemistry* / Q000378:metabolism; D002942:Circular Dichroism; D006418:Heme / Q000737:chemistry* / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D051379:Mice; D018625:Microscopy, Atomic Force; D009211:Myoglobin / Q000737:chemistry* / Q000378:metabolism; D041681:NIH 3T3 Cells; D011485:Protein Binding; D011487:Protein Conformation; D017550:Spectroscopy, Fourier Transform Infrared; D014466:Ultraviolet Rays
chemical_list: D000682:Amyloid; D001059:Apoproteins; D009211:Myoglobin; C010857:apomyoglobin; D006418:Heme