Extra N-terminal residues have a profound effect on the aggregation properties of the potential yeast prion protein Mca1.
The metacaspase Mca1 from Saccharomyces cerevisiae displays a Q/N-rich region at its N-terminus reminiscent of yeast prion proteins. In this study, we show that the ability of Mca1 to form insoluble aggregates is modulated by a peptide stretch preceding its putative prion-forming domain. Based on its genomic locus, three potential translational start sites of Mca1 can give rise to two slightly different long Mca1 proteins or a short version, Mca1(451/453) and Mca1(432,) respectively, although under normal physiological conditions Mca1(432) is the predominant form expressed. All Mca1 variants exhibit the Q/N-rich regions, while only the long variants Mca1(451/453) share an extra stretch of 19 amino acids at their N-terminal end. Strikingly, only long versions of Mca1 but not Mca1(432) revealed pronounced aggregation in vivo and displayed prion-like properties when fused to the C-terminal domain of Sup35 suggesting that the N-terminal peptide element promotes the conformational switch of Mca1 protein into an insoluble state. Transfer of the 19 N-terminal amino acid stretch of Mca1(451) to the N-terminus of firefly luciferase resulted in increased aggregation of luciferase, suggesting a protein destabilizing function of the peptide element. We conclude that the aggregation propensity of the potential yeast prion protein Mca1 in vivo is strongly accelerated by a short peptide segment preceding its Q/N-rich region and we speculate that such a conformational switch might occur in vivo via the usage of alternative translational start sites.
Erhardt
Marc
M
Molekulare Mikrobiologie, Fachbereich Biologie, Universität Konstanz, Konstanz, Germany.
Wegrzyn
Renee D
RD
Deuerling
Elke
E
D000483:Alleles; D000595:Amino Acid Sequence; D001665:Binding Sites; D020169:Caspases / Q000737:chemistry*; D049452:Green Fluorescent Proteins / Q000737:chemistry; D008856:Microscopy, Fluorescence / Q000379:methods; D008969:Molecular Sequence Data; D010454:Peptide Termination Factors / Q000737:chemistry; D010641:Phenotype; D011328:Prions / Q000737:chemistry*; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry*; D013045:Species Specificity
D010454:Peptide Termination Factors; D011328:Prions; C068068:SUP35 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D049452:Green Fluorescent Proteins; D020169:Caspases; C456272:MCA1 protein, S cerevisiae