Non-conventional protein secretionin yeast

The wheat powdery mildew genome shows the unique evolution of an obligate biotroph

“…hordei genes allowed us to identify 165 novel genes that had no homologs in other fungi and lacked a sequence encoding a signal peptide but had a dN/dS ratio greater than 0.5. We propose that these genes may encode candidate effector proteins (CEPs; Supplementary Note) that are either non-secreted or secreted by non-conventional pathways 20 . Taking CSEP and CEP genes together, B. graminis f.sp.…”

Straying off the Highway: Trafficking of Secreted Plant Proteins and Complexity in the Plant Cell Wall Proteome

“…Nonclassical or leaderless secretion was first described 20 years ago for two mammalian proteins (Cooper and Barondes, 1990;Rubartelli et al, 1990) and since then considerable progress has been made in characterizing a number of different pathways (Fig. 2) in mammalian and yeast cells, which will not be described in detail here (for review, see Nombela et al, 2006;Nickel and Seedorf, 2008;Prudovsky et al, 2008;Nickel and Rabouille, 2009). It therefore seems likely that nonclassical secretion is common to all eukaryotes, including plants, although this field is essentially unexplored.…”

Extraction of cell surface‐associated proteins from living yeast cells

“…We also show that the extraction temperature is important because, in contrast to what happens at 37 • C, β-mercaptoethanol-induced release of proteins into the extraction solution is minimal at 4 • C. When analysed by SDS-PAGE, β-mercaptoethanol extracts of living cells obtained at 37 • C contain dozens of low-molecular-mass, sharply delineated bands (Casanova et al, 1992;Vediyappan et al, 2000; Figure 1), consistent with the notion that they represent cytosolic proteins. Such extracts are enriched with glycolytic enzymes, elongation factors and folding proteins (reviewed in Nombela et al, 2006). This is consistent with β-mercaptoethanol-induced cell leakage, because these three categories of proteins are the most abundant cytosolic proteins, with copy numbers varying between a few hundred thousands to more than one-and-a-half million per cell; note that it has been estimated that the large majority of proteins have an average copy number of ∼10 000/cell (Futcher et al, 1999).…”

“…This procedure is expected to release: (a) disulphide bridge-linked cell wall proteins because of the presence of the reducing agent; (b) non-covalently linked cell wall proteins such as Bgl2p (Cappellaro et al, 1998), because the affinity for cell wall polysaccharides is probably pH-dependent; (c) periplasmic proteins such as invertase, because the cell wall becomes more permeable after being treated with reducing agents (De 254 F. M. Klis et al Nobel et al, 1989Nobel et al, , 1990; and (d) ionically associated proteins, because most yeast proteins have a pKa <8 and become negatively charged in the alkaline extraction solution, thus losing their ability to bind to the negative charges of the cell wall glycoproteins. Surprisingly, such extracts often contain a wide variety of non-glycosylated cytosolic proteins, such as glycolytic enzymes, heat shock proteins and elongation factors (reviewed in Chaffin et al, 1998;Nombela et al, 2006). To explain their presence in these extracts and other similar observations, it has been proposed that yeasts possess a non-conventional protein export pathway for the transfer of cytosolic proteins over the plasma membrane.…”