Present address: Department of Chemistry, University of Florida, Gainesville, FL 32611, USA.
The Sup35 domains required for maintenance of weak, strong or undifferentiated yeast [PSI+] prions
Article first published online: 18 FEB 2004
Volume 51, Issue 6, pages 1649–1659, March 2004
How to Cite
Bradley, M. E. and Liebman, S. W. (2004), The Sup35 domains required for maintenance of weak, strong or undifferentiated yeast [PSI+] prions. Molecular Microbiology, 51: 1649–1659. doi: 10.1111/j.1365-2958.2003.03955.x
- Issue published online: 18 FEB 2004
- Article first published online: 18 FEB 2004
- Accepted 24 November, 2003.
The Sup35 protein can exist in a non-infectious form or in various infectious forms called [PSI+] prion variants (or prion strains). Each of the different [PSI+] prion variants converts non-infectious Sup35 molecules into that prion variant's infectious form. One definition of a ‘prion domain’ is the minimal fragment of a prion protein that is necessary and sufficient to maintain the prion form. We now demonstrate that the Sup35 N region (residues 1–123), which is frequently referred to as the ‘prion domain’, is insufficient to maintain the weak or strong [PSI +] variants per se, but appears to maintain them in an ‘undifferentiated’[PSI+] state that can differentiate into weak or strong [PSI+] variants when transferred to the full-length Sup35 protein. In contrast, Sup35 residues 1–137 are necessary and sufficient to faithfully maintain weak or strong [PSI+] variants. This implicates Sup35 residues 124–137 in the variant-specific maintenance of the weak or strong [PSI+] forms. Structure predictions indicate that the residues in the 124–137 region form an α-helix and that the 1–123 region may have β structure. In view of these findings, we discuss a plausible molecular basis for the [PSI+] prion variants as well as the inherent difficulties in defining a ‘prion domain’.