Structural Basis of Vta1 Function in the Multivesicular Body Sorting Pathway

SummaryThe MVB pathway plays essential roles in several eukaryotic cellular processes. Proper function of the MVB pathway requires reversible membrane association of the ESCRTs, a process catalyzed by Vps4 ATPase. Vta1 regulates the Vps4 activity, but its mechanism of action was poorly understood. We report the high-resolution crystal structures of the Did2- and Vps60-binding N-terminal domain and the Vps4-binding C-terminal domain of S. cerevisiae Vta1. The C-terminal domain also mediates Vta1 dimerization and both subunits are required for its function as a Vps4 regulator. Emerging from our analysis is a mechanism of regulation by Vta1 in which the C-terminal domain stabilizes the ATP-dependent double ring assembly of Vps4. In addition, the MIT motif-containing N-terminal domain, projected by a long disordered linker, allows contact between the Vps4 disassembly machinery and the accessory ESCRT-III proteins. This provides an additional level of regulation and coordination for ESCRT-III assembly and disassembly

Comparative proteomic analysis of indica and japonica rice varieties

Indica and japonica are two main subspecies of Asian cultivated rice (Oryza sativa L.) that differ clearly in morphological and agronomic traits, in physiological and biochemical characteristics and in their genomic structure. However, the proteins and genes responsible for these differences remain poorly characterized. In this study, proteomic tools, including two-dimensional electrophoresis and mass spectrometry, were used to globally identify proteins that differed between two sequenced rice varieties (93-11 and Nipponbare). In all, 47 proteins that differed significantly between 93-11 and Nipponbare were identified using mass spectrometry and database searches. Interestingly, seven proteins were expressed only in Nipponbare and one protein was expressed specifically in 93-11; these differences were confirmed by quantitative real-time PCR and proteomic analysis of other indica and japonica rice varieties. This is the first report to successfully demonstrate differences in the protein composition of indica and japonica rice varieties and to identify candidate proteins and genes for future investigation of their roles in the differentiation of indica and japonica rice

Protein profile of rice (Oryza sativa) seeds

Seeds are the most important plant storage organ and play a central role in the life cycle of plants. Since little is known about the protein composition of rice (Oryza sativa) seeds, in this work we used proteomic methods to obtain a reference map of rice seed proteins and identify important molecules. Overall, 480 reproducible protein spots were detected by two-dimensional electrophoresis on pH 4-7 gels and 302 proteins were identified by MALDI-TOF MS and database searches. Together, these proteins represented 252 gene products and were classified into 12 functional categories, most of which were involved in metabolic pathways. Database searches combined with hydropathy plots and gene ontology analysis showed that most rice seed proteins were hydrophilic and were related to binding, catalytic, cellular or metabolic processes. These results expand our knowledge of the rice proteome and improve our understanding of the cellular biology of rice seeds

Molecular and Physiological Characterization of Two Novel Multirepeat β-Thymosins from Silkworm, Bombyx mori.

β-thymosin plays important roles in the development of the lymphatic system and the central nervous system in vertebrates. However, its role and function in invertebrates remain much less explored. Here, we firstly isolated a gene encoding β-thymosin in silkworm (Bombyx mori L.). Interestingly, this gene encodes two polypeptides, named as BmTHY1 and BmTHY2, via two different modes of RNA splicing. The recombinant proteins fused with an N-term GST tag were over-expressed in Escherichia coli (E. coli) and further purified to near homogenity to prepare mouse antibodies. The Western blot analysis showed that these proteins were expressed in various tissues and organs, as well as in different developmental stages. Amazingly, the expression of BmTHY2 was hugely increased during the pupae stage, indicating a specialized role in this period. The expression of these proteins was gradually decreased in BmN cells infected by BmNPV, suggesting they may play different roles in the virus infection. In addition, both BmTHY1 and BmTHY2 can interact with 14-3-3 of silkworm and Ubiquitin of BmNPV as shown by GST pull down and Co-IP assays, consistent with their roles in the regulation of the development of nervous system

Molecular cloning, expression and characterization of Bmserpin-2 gene from Bombyx mori

Serpins are a broadly distributed family of protease inhibitors. In this study, the gene encoding Bombyx mori serpin-2 (Bmserpin-2) was cloned and expressed in E. coli. The Bmserpin-2 cDNA contains a 1125 bp open reading frame (ORF). The deduced protein has 374 amino-acid residues, contains a conserved SERPIN domain and shares extensive homology with other invertebrate serpins. RT-PCR analysis showed that Bmserpin-2 was expressed in all developmental stages of B. mori larvae and various larval tissues. Subcellular localization analysis indicated that Bmserpin-2 protein was located in the cytoplasm. Interestingly, real-time quantitative PCR revealed that the expression of Bmserpin-2 in the midgut of susceptible B. mori strain 306 significantly increased at 72 hours post inoculation (hpi) when infected with BmNPV. However, there was no significant increase of the Bmserpin-2 expression in resistant strain NB infected with BmNPV. Thus, our data indicates that Bmserpin-2 may be involved in B. mori antiviral response

Proteomic profiling of liver from Elaphe taeniura, a common snake in eastern and southeastern Asia

Snake liver has been implicated in the adaptation of snakes to a variety of habitats. However, to date, there has been no systematic analysis of snake liver proteins. In this study, we undertook a proteomic analysis of liver from the colubrid snake Elaphe taeniura using a combination of two-dimensional electrophoresis (2-DE) and matrix-assisted laser desorption/ionization time of flightmass spectrometry (MALDI-TOF MS). We also constructed a local protein sequence database based on transcriptome sequencing to facilitate protein identification. Of the 268 protein spots revealed by 2-DE 109 gave positive MS signals, 84 of which were identified by searching the NCBInr, Swiss-Prot and local databases. The other 25 protein spots could not be identified, possibly because their transcripts were not be stable enough to be detected by transcriptome sequencing. GO analysis showed that most proteins may be involved in binding, catalysis, cellular processes and metabolic processes. Forty-two of the liver proteins identified were found in other reptiles and in amphibians. The findings of this study provide a good reference map of snake liver proteins that will be useful in molecular investigations of snake physiology and adaptation

The Spatiotemporal expression profiles of BmTHYs.

<p>Western blot analysis of the expression levels of BmTHYs in different developmental stage (A) and in different tissues and organs (B). The mass of each lane’s total protein were 50 μg, and the sample were equalized. (A) Lane 1: egg; Lane 2: 1st instar; Lane 3: 2nd instar; Lane 4: 3rd instar; Lane 5: 4th instar; Lane 6: 5th instar; Lane 7: pupae; Lane 8: moth. (B) Lane 1: midgut; Lane 2: testis; Lane 3: ovary; Lane 4: head; Lane 5: fat body; Lane 6: hemolymph.</p

The expression pattern of BmTHYs in BmN cells infected with BmNPV.

<p>The BmN cells were infected with BmNPV and samples were collected at different hours to examine the expression of BmTHYs. The mass of each lane’s total protein were 30 μg, and the sample were equalized.</p