Prion Amyloid Polymorphs - The Tag Might Change It All

Area of Science:

• Biochemistry
• Structural Biology
• Molecular Biology

Background:

• Sup35p protein from Saccharomyces cerevisiae propagates via a prion-like mechanism, forming insoluble fibrils from soluble precursors.
• Sup35p comprises N, M, and globular domains; previous studies on tagged NM constructs showed discrepancies in fibril conformation.

Purpose of the Study:

• To investigate the structural impact of C-terminal polyhistidine tags on Sup35p NM fibrils using solid-state NMR.
• To compare fibril conformations of untagged, N-terminally tagged, and C-terminally tagged Sup35p NM constructs.

Main Methods:

• Solid-state Nuclear Magnetic Resonance (NMR) spectroscopy was employed.
• Fibrils from untagged and C-terminally polyhistidine-tagged Sup35p NM constructs were analyzed.

Main Results:

• The conformation of untagged Sup35p NM fibrils closely matched N-terminally tagged versions, validating prior findings.
• A C-terminal polyhistidine tag drastically altered the NM fibril structure, consistent with previous literature on this construct.
• Modifications at the C-terminus, even small tags, exerted a substantial and unexpected influence on fibril structure and [PSI+] induction propensity.

Conclusions:

• The C-terminally located globular domain of Sup35p influences the N-domain fibrillar core structure.
• C-terminal tags on Sup35p NM significantly impact fibril structure and the protein's ability to induce the [PSI+] prion state.