Editing Sup35p (section)

==Physical Characteristics==

Sup 35 contains a carboxyl-terminal region ([[C-terminus]]), which is responsible for the translation-termination activity. The amino-terminal([[N-terminus]]) region of the protein is responsible for alternately folding depending on the conformation. The middle (m) domain has an unknown function. In an effort to determine the function of these N and M regions, in Susan Lindquists' experiment two of the strains were engineered to produce a version of Sup35p which does not include the N and M regions.<ref name="pmid11331577">{{cite journal | vauthors = Parham SN, Resende CG, Tuite MF | title = Oligopeptide repeats in the yeast protein Sup35p stabilize intermolecular prion interactions | journal = The EMBO Journal | volume = 20 | issue = 9 | pages = 2111–9 | date = May 2001 | pmid = 11331577 | pmc = 125439 | doi = 10.1093/emboj/20.9.2111 }}</ref>

The Sup35p protein is 685 amino acids long.<ref>{{cite web | title = Sup35p [Saccharomyces cerevisiae] | publisher = National Center for Biotechnology Information, U.S. National Library of Medicine | url = https://www.ncbi.nlm.nih.gov/protein/AHX83123.1 }}</ref> The C-terminal contains 5 complete and one incomplete repeat of the [[Oligopeptide repeat]] sequence PQGGYQQ-YN. In modified versions of the gene, it has been shown that the more repeats of this sequence present, the more the protein is to assume the [Psi+] confirmation. In fact, the addition of two extra repeats (R2) result in the [Psi-] to [Psi+] conversion in being 5000 times faster.<ref name="pmid11331577"/> PMN2, a mutant, dominant version of the gene Sup35p, has a glycine to aspartic acid substitution in the second repeat. The resulting [[phenotype]] is a lack of ability to maintain the [Psi+] conformation.

The N-terminus has a high glutamine/asparagine amount at 43%, while the average yeast protein only contains 9%. The N terminus is 114 amino acids long and is termed the prion forming domain (PrD). Over expression of the Sup35p gene can lead to [Psi+].

Both the N and M terminals and the C terminus form binding sites to Sup45p, giving a total of two. Also, in binding to Sup45p the [psi+] protein can cause it to aggregate and form a prion.<ref name="pmid9111351">{{cite journal | vauthors = Paushkin SV, Kushnirov VV, Smirnov VN, Ter-Avanesyan MD | title = Interaction between yeast Sup45p (eRF1) and Sup35p (eRF3) polypeptide chain release factors: implications for prion-dependent regulation | journal = Molecular and Cellular Biology | volume = 17 | issue = 5 | pages = 2798–805 | date = May 1997 | pmid = 9111351 | pmc = 232131 | doi = 10.1128/mcb.17.5.2798 }}</ref>