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

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Principles Of Fluorescence Spectroscopy

The Hsp70 and Hsp60 chaperone machines.

Since the discovery of SNARE proteins in the late 1980s, SNAREs have been recognized as key components of protein complexes that drive membrane fusion. Despite considerable sequence divergence among SNARE proteins, their mechanism seems to be conserved and is adaptable for fusion reactions as diverse as those involved in cell growth, membrane repair, cytokinesis and synaptic transmission. A fascinating picture of these robust nanomachines is emerging.

/pdf/snares-engines-for-membrane-fusion-dircca11bk.pdf

SNAREs--engines for membrane fusion.

T URNOVER OF AB ERR ANT PROT EINS IN E. COLI . . . . . . . . . . . . . . . . . 445 The Lon Protease . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 446 DnaK. DnaJ. GrpE. GroEL and GroES . . . . . . . . . . . . . . . . . . . . . . . . . . 447 The Clp Protease . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 448 The DegP Protease . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 452

The Function of Heat-Shock Proteins in Stress Tolerance: Degradation and Reactivation of Damaged Proteins

The survival of any microbe relies upon its ability to respond to environmental change. Use of Extra Cytoplasmic Function (ECF) RNA polymerase sigma (σ) factors is a major strategy enabling dynamic responses to extracellular signals. Streptomyces species harbor a large number of ECF σ factors; nearly all of which regulate genes required for morphological differentiation and/or response to environmental stress, except for σAntA, which regulates starter-unit biosynthesis in the production of antimycin, an anticancer compound. Unlike a canonical ECF σ factor, whose activity is regulated by a cognate anti-σ factor, σAntA is an orphan, raising intriguing questions about how its activity may be controlled. Here, we reconstitute in vitro ClpXP proteolysis of σAntA, but not a variant lacking a C-terminal di-alanine motif. Furthermore, we show that the abundance of σAntAin vivo is enhanced by removal of the ClpXP recognition sequence, and that levels of the protein rise when cellular ClpXP protease activity is abolished. These data establish direct proteolysis as an alternative and thus far unique control strategy for an ECF RNA polymerase σ factor and expands the paradigmatic understanding of microbial signal transduction regulation. Importance Natural products produced by Streptomyces species underpin many industrially- and medically-important compounds. However, the majority of the ~30 biosynthetic pathways harboured by an average species are not expressed in the laboratory. This undiscovered biochemical diversity is believed to comprise an untapped resource for natural products drug discovery. A major roadblock preventing the exploitation of unexpressed biosynthetic pathways is a lack of insight into their regulation and limited technology for activating their expression. Our findings reveal that the abundance of σAntA, which is the cluster-situated regulator of antimycin biosynthesis, is controlled by the ClpXP protease. These data link proteolysis to the regulation of natural product biosynthesis for the first time and we anticipate that this will emerge as a major strategy by which actinobacteria regulate production of their natural products. Further study of this process will advance understanding of how expression of secondary metabolism is controlled and will aid pursuit of activating unexpressed biosynthetic pathways.

https://www.biorxiv.org/content/biorxiv/early/2020/02/07/576462.full.pdf

Tania A. Baker

Papers

Regulation of antimycin biosynthesis is controlled by the ClpXP protease