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

J. Appl. Cryst.の発刊に際して

BIOE 402. Medical Technology Assessment. 2 or 3 hours. Bioentrepreneur course. Assessment of medical technology in the context of commercialization. Objectives, competition, market share, funding, pricing, manufacturing, growth, and intellectual property; many issues unique to biomedical products. Course Information: 2 undergraduate hours. 3 graduate hours. Prerequisite(s): Junior standing or above and consent of the instructor.

“Bioinformatics” 특집을 내면서

RELION: implementation of a Bayesian approach to cryo-EM structure determination.

Regulation of Translation Initiation in Eukaryotes: Mechanisms and Biological Targets

The crystal structure of the bacterial 70S ribosome refined to 2.8 angstrom resolution reveals atomic details of its interactions with messenger RNA (mRNA) and transfer RNA (tRNA). A metal ion stabilizes a kink in the mRNA that demarcates the boundary between A and P sites, which is potentially important to prevent slippage of mRNA. Metal ions also stabilize the intersubunit interface. The interactions of E-site tRNA with the 50S subunit have both similarities and differences compared to those in the archaeal ribosome. The structure also rationalizes much biochemical and genetic data on translation.

https://science.sciencemag.org/content/sci/313/5795/1935.full.pdf

Structure of the 70S Ribosome Complexed with mRNA and tRNA

Elongation factor G (EF-G) is a guanosine triphosphatase (GTPase) that plays a crucial role in the translocation of transfer RNAs (tRNAs) and messenger RNA (mRNA) during translation by the ribosome. We report a crystal structure refined to 3.6 angstrom resolution of the ribosome trapped with EF-G in the posttranslocational state using the antibiotic fusidic acid. Fusidic acid traps EF-G in a conformation intermediate between the guanosine triphosphate and guanosine diphosphate forms. The interaction of EF-G with ribosomal elements implicated in stimulating catalysis, such as the L10-L12 stalk and the L11 region, and of domain IV of EF-G with the tRNA at the peptidyl-tRNA binding site (P site) and with mRNA shed light on the role of these elements in EF-G function. The stabilization of the mobile stalks of the ribosome also results in a more complete description of its structure.

/pdf/the-structure-of-the-ribosome-with-elongation-factor-g-fvngmkq0tl.pdf

The structure of the ribosome with elongation factor G trapped in the posttranslocational state.

http://www.biochem.emory.edu/dunham/documents/Petry%20et%20al.,%20Cell%202005.pdf

Crystal structures of the ribosome in complex with release factors RF1 and RF2 bound to a cognate stop codon.

Ribosome recycling factor (RRF), together with elongation factor G (EF-G), catalyzes recycling of ribosomes after one round of protein synthesis. The crystal structure of RRF was determined at 2.55 angstrom resolution. The protein has an unusual fold where domain I is a long three-helix bundle and domain II is a three-layer beta/alpha/beta sandwich. The molecule superimposes almost perfectly with a transfer RNA (tRNA) except that the amino acid-binding 3' end is missing. The mimicry suggests that RRF interacts with the posttermination ribosomal complex in a similar manner to a tRNA, leading to disassembly of the complex. The structural arrangement of this mimicry is entirely different from that of other cases of less pronounced mimicry of tRNA so far described.

https://science.sciencemag.org/content/sci/286/5448/2349.full.pdf

Crystal structure of Thermotoga maritima ribosome recycling factor: a tRNA mimic.

Ribosome recycling factor (RRF) together with elongation factor G (EF-G) disassembles the post- termination ribosomal complex. Inhibitors of translocation, thiostrepton, viomycin and aminoglycosides, inhibited the release of tRNA and mRNA from the post-termination complex. In contrast, fusidic acid and a GTP analog that fix EF-G to the ribosome, allowing one round of tRNA translocation, inhibited mRNA but not tRNA release from the complex. The release of tRNA is a prerequisite for mRNA release but partially takes place with EF-G alone. The data are consistent with the notion that RRF binds to the A-site and is translocated to the P-site, releasing deacylated tRNA from the P- and E-sites. The final step, the release of mRNA, is accompanied by the release of RRF and EF-G from the ribosome. With the model post-termination complex, 70S ribosomes were released from the post-termination complex by the RRF reaction and were then dissociated into subunits by IF3.

Maria Selmer

Papers

Structure of the 70S Ribosome Complexed with mRNA and tRNA

The structure of the ribosome with elongation factor G trapped in the posttranslocational state.

Crystal structures of the ribosome in complex with release factors RF1 and RF2 bound to a cognate stop codon.

Crystal structure of Thermotoga maritima ribosome recycling factor: a tRNA mimic.

Post-termination complex disassembly by ribosome recycling factor, a functional tRNA mimic.