抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

https://archive-ouverte.unige.ch/unige:18229/ATTACHMENT01

TOR signaling in growth and metabolism.

In certain aspects, the invention relates to methods for identifying compounds which modulate Akt activity mediated by the rictor-mTOR complex and methods for treating or preventing a disorder that is associated with aberrant Akt activity.

http://science.sciencemag.org/content/sci/307/5712/1098.full.pdf

Phosphorylation and regulation of Akt/PKB by the rictor-mTOR complex

We sought to create a comprehensive catalog of yeast genes whose transcript levels vary periodically within the cell cycle. To this end, we used DNA microarrays and samples from yeast cultures sync...

Comprehensive Identification of Cell Cycle–regulated Genes of the Yeast Saccharomyces cerevisiae by Microarray Hybridization

Multiplexed Protein Quantitation in Saccharomyces cerevisiae Using Amine-reactive Isobaric Tagging Reagents

Gain of function in an ERV/ALR sulfhydryl oxidase by molecular engineering of the shuttle disulfide.

Intracellular sorting of the general amino acid permease (Gap1p) in Saccharomyces cerevisiae depends on availability of amino acids such that at low amino acid concentrations Gap1p is sorted to the plasma membrane, whereas at high concentrations Gap1p is sorted to the vacuole. In a genome-wide screen for mutations that affect Gap1p sorting we identified deletions in a subset of components of the ESCRT (endosomal sorting complex required for transport) complex, which is required for formation of the multivesicular endosome (MVE). Gap1p-GFP is delivered to the vacuolar interior by the MVE pathway in wild-type cells, but when formation of the MVE is blocked by mutation, Gap1p-GFP efficiently cycles from this compartment to the plasma membrane, resulting in unusually high permease activity at the cell surface. Importantly, cycling of Gap1p-GFP to the plasma membrane is blocked by high amino acid concentrations, defining recycling from the endosome as a major step in Gap1p trafficking under physiological control. Mutations in LST4 and LST7 genes, previously identified for their role in Gap1p sorting, similarly block MVE to plasma membrane trafficking of Gap1p. However, mutations in other recycling complexes such as the retromer had no significant effect on the intracellular sorting of Gap1p, suggesting that Gap1p follows a genetically distinct pathway for recycling. We previously found that Gap1p sorting from the Golgi to the endosome requires ubiquitination of Gap1p by an Rsp5p ubiquitin ligase complex, but amino acid abundance does not appear to significantly alter the accumulation of polyubiquitinated Gap1p. Thus the role of ubiquitination appears to be a signal for delivery of Gap1p to the MVE, whereas amino acid abundance appears to control the cycling of Gap1p from the MVE to the plasma membrane.

/pdf/amino-acids-regulate-retrieval-of-the-yeast-general-amino-3ijle1bgaz.pdf

Amino Acids Regulate Retrieval of the Yeast General Amino Acid Permease from the Vacuolar Targeting Pathway

The membrane-associated flavoprotein Ero1p promotes disulfide bond formation in the endoplasmic reticulum (ER) by selectively oxidizing the soluble oxidoreductase protein disulfide isomerase (Pdi1p), which in turn can directly oxidize secretory proteins. Two redox-active disulfide bonds are essential for Ero1p oxidase activity: Cys100-Cys105 and Cys352-Cys355. Genetic and structural data indicate a disulfide bond is transferred from Cys100-Cys105 directly to Pdi1p, whereas a Cys352-Cys355 disulfide bond is used to reoxidize the reduced Cys100-Cys105 pair through an internal thiol-transfer reaction. Electron transfer from Cys352-Cys355 to molecular oxygen, by way of a flavin cofactor, maintains Cys352-Cys355 in an oxidized form. Herein, we identify a mixed disulfide species that confirms the Ero1p intercysteine thiol-transfer relay in vivo and identify Cys105 and Cys352 as the cysteines that mediate thiol-disulfide exchange. Moreover, we describe Ero1p mutants that have the surprising ability to oxidize substrates in the absence of Cys100-Cys105. We show the oxidase activity of these mutants results from structural changes in Ero1p that allow substrates increased access to Cys352-Cys355, which are normally buried beneath the protein surface. The altered activity of these Ero1p mutants toward selected substrates leads us to propose the catalytic mechanism involving transfer between cysteine pairs evolved to impart substrate specificity to Ero1p.

/pdf/disulfide-transfer-between-two-conserved-cysteine-pairs-223c60e7o7.pdf

Disulfide Transfer between Two Conserved Cysteine Pairs Imparts Selectivity to Protein Oxidation by Ero1

I. INTRODUCTION A growing yeast cell doubles its surface area every division cycle. The principal function of the yeast secretory pathway is to generate and deliver new membrane and protein to the growing surface of the bud. The pathway that newly synthesized proteins follow to the cell surface has the same outline in Saccharomyces cerevisiae as that originally defined in mammalian cells (Palade 1975). The principal steps in the pathway are outlined below and are diagrammed in Figure 1. The gene products responsible for the function of the secretory pathway are given at the end of this chapter in Table 1. Secretory proteins are translocated from the cytosol into the lumen of the endoplasmic reticulum (ER). For some proteins, translocation occurs cotranslationally and for other proteins, translocation can occur posttranslationally, i.e., after completion of protein synthesis. Secretory proteins assume a functional conformation within the lumen of the ER. This can involve covalent modifications of the protein such as cleavage of signal peptide, addition of N-linked and O-linked carbohydrate chains, disulfide bond formation, and addition of glycosylphosphatidylinositol (GPI) anchors. Catalyzed protein folding and, in some cases, assembly of multimeric protein complexes also take place in the ER lumen. Secretory proteins are then packaged into 60-nm vesicles that bud from the ER. These vesicles then deliver their contents to the Golgi by fusion with the Golgi membrane. The Golgi apparatus is composed of three biochemically distinguishable compartments. Secretory proteins are carried through successive compartments of the Golgi...

2 Protein Secretion, Membrane Biogenesis, and Endocytosis

The endoplasmic reticulum (ER) provides an environment optimized for oxidative protein folding through the action of Ero1p, which generates disulfide bonds, and Pdi1p, which receives disulfide bonds from Ero1p and transfers them to substrate proteins. Feedback regulation of Ero1p through reduction and oxidation of regulatory bonds within Ero1p is essential for maintaining the proper redox balance in the ER. In this paper, we show that Pdi1p is the key regulator of Ero1p activity. Reduced Pdi1p resulted in the activation of Ero1p by direct reduction of Ero1p regulatory bonds. Conversely, upon depletion of thiol substrates and accumulation of oxidized Pdi1p, Ero1p was inactivated by both autonomous oxidation and Pdi1p-mediated oxidation of Ero1p regulatory bonds. Pdi1p responded to the availability of free thiols and the relative levels of reduced and oxidized glutathione in the ER to control Ero1p activity and ensure that cells generate the minimum number of disulfide bonds needed for efficient oxidative protein folding.

https://rupress.org/jcb/article-pdf/196/6/713/1355597/jcb_201110090.pdf

Chris A. Kaiser

Papers

Gain of function in an ERV/ALR sulfhydryl oxidase by molecular engineering of the shuttle disulfide.

Amino Acids Regulate Retrieval of the Yeast General Amino Acid Permease from the Vacuolar Targeting Pathway

Disulfide Transfer between Two Conserved Cysteine Pairs Imparts Selectivity to Protein Oxidation by Ero1

2 Protein Secretion, Membrane Biogenesis, and Endocytosis

Balanced Ero1 activation and inactivation establishes ER redox homeostasis