Structural studies on chimeric Sesbania mosaic virus coat protein: Revisiting SeMV assembly

The capsid protein (CP) of Sesbania mosaic virus (SeMV, a T=3 plant virus) consists of a disordered N-terminal R-domain and an ordered S-domain. Removal of the R-domain results in the formation of T=1 particles. In the current study, the R-domain was replaced with unrelated polypeptides of similar lengths: the B-domain of Staphylococcus aureus SpA, and SeMV encoded polypeptides P8 and P10. The chimeric proteins contained T=3 or larger virus-like particles (VLPs) and could not be crystallized. The presence of metal ions during purification resulted in a large number of heterogeneous nucleoprotein complexes. N Delta 65-B (R domain replaced with B domain) could also be purified in a dimeric form. Its crystal structure revealed T=1 particles devoid of metal ions and the B-domain was disordered. However, the B-domain was functional in N Delta 65-B VLPs, suggesting possible biotechnological applications. These studies illustrate the importance of N-terminal residues, metal ions and robustness of the assembly process. (C) 2015 Elsevier Inc. All rights reserved.

Multiple oligomeric structures of a bacterial small heat shock protein

Small heat shock proteins are ubiquitous molecular chaperones that form the first line of defence against the detrimental effects of cellular stress. Under conditions of stress they undergo drastic conformational rearrangements in order to bind to misfolded substrate proteins and prevent cellular protein aggregation. Owing to the dynamic nature of small heat shock protein oligomers, elucidating the structural basis of chaperone action and oligomerization still remains a challenge. In order to understand the organization of sHSP oligomers, we have determined crystal structures of a small heat shock protein from Salmonella typhimurium in a dimeric form and two higher oligomeric forms: an 18-mer and a 24-mer. Though the core dimer structure is conserved in all the forms, structural heterogeneity arises due to variation in the terminal regions.

A Deep-Blue Electroluminescent Device Based on a Coumarin Derivative

The design and synthesis is reported of 7-(9H-carbazol-9-yl)-4-methylcoumarin (Cz-Cm), comprising a carbazole donor moiety and a 4-methylcoumarin acceptor unit, for use in a blue organic light-emitting diode. A detailed solid state, theoretical and spectroscopic study was performed to understand the structure-property relationships. The material exhibits deep-blue emission and high photoluminescence quantum yield both in solution and in a doped matrix. A deep-blue electroluminescence emission at 430nm, a maximum brightness of 292cdm(-2) and an external quantum efficiency of 0.4% was achieved with a device configured as follows: ITO/NPD (30nm)/TCTA (20nm)/CzSi(10nm)/10wt% Cz-Cm:DPEPO (10nm)/TPBI (30nm)/LiF (1nm)/Al ITO=indium tin oxide, NPD=N,N-di(1-naphthyl)-N,N-diphenyl-(1,1-biphenyl)-4,4-diamine, TCTA=tris(4-carbazoyl-9-ylphenyl)amine, CzSi=9-(4-tert-butylphenyl)-3,6-bis(triphenylsilyl)-9H-carbazole, DPEPO=bis2-(diphenylphosphino)phenyl]ether oxide, TPBI=1,3,5-tris(N-phenylbenzimidazol-2-yl)benzene].

Mass spectrometric analysis of dimer-disrupting mutations in Plasmodium triosephosphate isomerase

Electrospray ionization mass spectrometry (ESI MS) under nanospray conditions has been used to examine the effects of mutation at two key dimer interface residues, Gln (Q) 64 and Thr (T) 75, in Plasmodium falciparum triosephosphate isomerase. Both residues participate in an intricate network of intra- and intersubunit hydrogen bonds. The gas phase distributions of dimeric and monomeric protein species have been examined for the wild type enzyme (TWT) and three mutants, Q64N, Q64E, and 175S, under a wide range of collision energies (40-160 eV). The results established the order of dimer stability as TWT > T75S > Q64E similar to Q64N. The mutational effects on dimer stability are in good agreement with the previously reported estimates, based on the concentration dependence of enzyme activity. Additional experiments in solution, using inhibition of activity by a synthetic dimer interface peptide, further support the broad agreement between gas phase and solution studies. (C) 2016 Elsevier Inc. All rights reserved.