分类: 生物学 >> 生物物理学 >> 生物物理、生物化学与分子生物学 提交时间: 2016-05-11
摘要: Eukaryotic genomes are organized hierarchically into chromatin structures by histones. Despite extensive research for over 30 years, not only the fundamental structure of the 30-nm chromatin fiber is being debated, but the actual existence of such fiber remains hotly contested. In this review, we focus on the most recent progress in elucidating the structure of the 30-nm fiber upon in vitro reconstitution, and its possible organization inside the nucleus. In addition, we discuss the roles of linker histone H1 as well as the importance of specific nucleosome-nucleosome interactions in the formation of the 30-nm fiber. Finally, we discuss the involvement of structural variations and epigenetic mechanisms available for the regulation of this chromatin form. (C) 2015 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.
分类: 生物学 >> 生物物理学 >> 生物力学与生物流变学 提交时间: 2016-05-11
摘要: Infectious bursal disease virus (IBDV) poses a significant threat to the poultry industry. Viral protein 2 (VP2), the major structural protein of IBDV, has been subjected to frequent mutations that have imparted tremendous genetic diversity to the virus. To determine how amino acid mutations may affect the virulence of IBDV, we built a structural model of VP2 of a very virulent strain of IBDV identified in China, vvIBDV Gx, and performed a molecular dynamics simulation of the interaction between virulence sites. The study showed that the amino acid substitutions that distinguish vvIBDV from attenuated IBDV (H253Q and T284A) favor a hydrophobic and flexible conformation of beta-barrel loops in VP2, which could promote interactions between the virus and potential IBDV-specific receptors. Population sequence analysis revealed that the IBDV strains prevalent in East Asia show a significant signal of positive selection at virulence sites 253 and 284. In addition, a signal of co-evolution between sites 253 and 284 was identified. These results suggest that changes in the virulence of IBDV may result from both the interaction and the co-evolution of multiple amino acid substitutions at virulence sites.
分类: 生物学 >> 生物物理学 >> 生物物理、生物化学与分子生物学 提交时间: 2016-05-12
摘要: The architecture and structural details of chromatin assembler, chromatin modifier, and chromatin remodeler, and their complexes with nucleosome and chromatin, are critical for revealing the molecular mechanisms for the establishment, maintenance and regulation of epigenetic information. The fast-developing cryo-electron microscopy (cryo-EM) provides an indispensible tool for the structure determiantion of the huge, multi-subunits, and flexible epigenetic regulation related macromolecular assemblies. In this review, we summarized the recent progresses on EM structural studies of macromolecules and complexes relating to epigenetic regulation.
分类: 生物学 >> 生物物理学 >> 免疫学 提交时间: 2016-05-11
摘要: Hemocyanins present in invertebrate hemolymph are multifunctional proteins, responsible for oxygen transport and contributing to innate immunity through phenoloxidase-like activity. In arthropods, hemocyanin has been identified as a source of broad-spectrum antimicrobial peptides during infection. Conversely, no hemocyanin-derived antimicrobial peptides have been reported for molluscs. The present study describes a putative antimicrobial region, termed haliotisin, located within the linking sequence between the alpha-helical domain and beta-sheet domain of abalone (Haliotis tuberculata) hemocyanin functional unit E. A series of synthetic peptides based on overlapping fragments of the haliotisin region were tested for their bactericidal potential. Incubating Gram-positive and Gram-negative bacteria in the presence of certain haliotisin peptides, notably peptides 3-4-5 (DTFDYKKFGYRYDSLELEGRS ISRIDELIQQRQEKDRTFAGFLLKGFGTSAS) led to reductions in microbial growth. Furthermore, transmission electron micrographs of haliotisin-treated bacteria revealed damages to the microbial cell wall. Data discussed here provides the first evidence to suggest that molluscan hemocyanin may act as a source of anti-infective peptides. (C) 2014 Elsevier Ltd. All rights reserved.