Linear Peptides—A Combinatorial Innovation in the Venom of Some Modern Spiders

In the venom of spiders, linear peptides (LPs), also called cytolytical or antimicrobial peptides, represent a largely neglected group of mostly membrane active substances that contribute in some spider species considerably to the killing power of spider venom. By next-generation sequencing venom gland transcriptome analysis, we investigated 48 spider species from 23 spider families and detected LPs in 20 species, belonging to five spider families (Ctenidae, Lycosidae, Oxyopidae, Pisauridae, and Zodariidae). The structural diversity is extraordinary high in some species: the lynx spider Oxyopes heterophthalmus contains 62 and the lycosid Pardosa palustris 60 different LPs. In total, we identified 524 linear peptide structures and some of them are in lycosids identical on amino acid level. LPs are mainly encoded in complex precursor structures in which, after the signal peptide and propeptide, 13 or more LPs (Hogna radiata) are connected by linkers. Besides Cupiennius species, also in Oxyopidae, posttranslational modifications of some precursor structures result in the formation of two-chain peptides. It is obvious that complex precursor structures represent a very suitable and fast method to produce a high number and a high diversity of bioactive LPs as economically as possible. At least in Lycosidae, Oxyopidae, and in the genus Cupiennius, LPs reach very high Transcripts Per Kilobase Million values, indicating functional importance within the envenomation process.

Complex precursor structures of cytolytic cupiennins identified in spider venom gland transcriptomes

Analysis of spider venom gland transcriptomes focuses on the identification of possible neurotoxins, proteins and enzymes. Here, the first comprehensive transcriptome analysis of cupiennins, small linear cationic peptides, also known as cytolytic or antimicrobial peptides, is reported from the venom gland transcriptome of Cupiennius salei by 454- and Illumina 3000 sequencing. Four transcript families with complex precursor structures are responsible for the expression of 179 linear peptides. Within the transcript families, after an anionic propeptide, cationic linear peptides are separated by anionic linkers, which are transcript family specific. The C-terminus of the transcript families is characterized by a linear peptide or truncated linkers with unknown function. A new identified posttranslational processing mechanism explains the presence of the two-chain CsTx-16 family in the venom. The high diversity of linear peptides in the venom of a spider and this unique synthesis process is at least genus specific as verified with Cupiennius getazi.

More than just a ticket canceller: the mitochondrial processing peptidase tailors complex precursor proteins at internal cleavage sites

The Mitochondrial processing peptidase (MPP) is well known for cleaving off N-terminal targeting signals from mitochondrial precursor proteins. Here we show that MPP also processes more complex precursors at internal cleavage sites, separating polyproteins into distinct functional enzymes. This function is conserved among eukaryotes.

Structure-guided discovery of a luminescent theranostic toolkit for living cancer cells and the imaging behavior effect

In order to optimise dual-functional theranostics for application in living systems, we developed an iridium(iii) theranostic by grafting an inhibitor as a “binding unit” onto an iridium(iii) complex precursor as a “signaling unit”.

Nano-sized BaSnO3 powder via a precursor route. Comparative study of sintering behaviour and mechanism of fine and coarse-grained powders.

Preparation of a very fine BaSnO3 powder by calcination of a barium tin 1,2-ethanediolato complex precursor and its sintering behaviour are described herein. A ratecontrolled calcination process to 820 °C leads to a nm-sized BaSnO3 powder with aspecific surface area of S = 15.1 m2/g (dav. = 55 nm). The powder has a slightly largercell parameter of a = 412.22(7) pm compared to the single crystal value, whichdecreases with increasing calcination temperature and reaches the reference value above1000 °C. The sintering behaviour is compared between fine- and coarse-grainedBaSnO3 powders. Corresponding powder compacts of the nano-sized BaSnO3 achieve arelative density of 90 % after sintering at 1600 °C for 1 h and at 1500 °C and a soakingtime of 30 h, whereas coarse-grained powder compacts reach only 80 % of the relative density at 1650 °C (10 h). Furthermore, the shrinkage mechanisms of fine and coarsegrainedpowder compacts have been investigated and are discussed.