Unique molecular architecture of egg case silk protein in a spider, Nephila clavata.

We describe a unique silk protein secreted from the cylindrical silk glands of the spider Nephila clavata. This silk is primarily composed of three proteins, whose transcripts of approximately 16.0, 14.5 and 13.0 kb are homologous to one another in two termini and repetitive units, as determined on Northern blotting. Its overall organization shows that it is similar to other characterized silk proteins, including in the mainly central repetitive region as well as the non-repetitive N-terminal (166 residues) and C-terminal (176 residues) parts. However, up to 90% of the protein consists of highly ordered repetitive structures that are not found in other silks. The repetitive region mainly consists of several types of complexes and remarkably conserved polypeptide repeats. The assembled repeat units (A1B1) contain a high proportion of Ala (30.41%), Ser (25.15%), and residues with hydrophobic side chains (22.22% for Gly, Leu, Ile, Val and Phe combined). The presence of Ser-rich and GVGAGASA motifs suggests the formation of a beta-sheet. The repetitive region is characterized by alternating arrays of hydrophobic and hydrophilic blocks. The results suggested that this egg case silk is an exceptional protein when compared with previously investigated spider silks.

Blind humans rely on muscle sense more than normally sighted humans for guiding goal-directed movement.

The purpose of this study was to investigate whether totally blind humans rely on muscle sense for guiding goal-directed movement more than do blindfolded normally sighted humans. Twelve totally blind humans and 12 blindfolded normally sighted humans performed goal-directed movement. The subjects rapidly extended the elbow to a target angle in response to an auditory start cue while a vibration was applied to the antagonist muscle. Verbal feedback, concerning whether the movement was terminated near the target angle, was given immediately after each trial. Through these trials, the subjects acquired a movement terminating near the target angle. Immediately after these trials, the same movement was performed 20 times without the vibration and the verbal feedback. In the trials without the vibration and verbal feedback, the terminal angle of the movement was overshot as a reference to the last 5 trials where there was the vibration and verbal feedback. The amount of overshooting in the blind humans was significantly larger than that in blindfolded normally sighted humans. These findings indicate that for guiding goal-directed movement blind humans rely on their muscle sense more than do normally sighted humans.

Expression of spider flagelliform silk protein in Bombyx mori cell line by a novel Bac-to-Bac/BmNPV baculovirus expression system.

Bombyx mori nuclear polyhedrosis virus (BmNPV) baculovirus expression system (BES) has a lot of advantages such as high expression efficiency, convenience, and low feeding cost. In this report, we used a recently developed BmNPV bacmid, which could infect both B. mori cell lines and silkworm larvae. The results showed it takes only 7 to 10 days to generate recombinant baculovirus and permit the rapid isolation from small-scale cultures and then use it to transfect B. mori cell lines, compared to traditional homologous recombination method, which needs at least 40 days for multiple rounds of purification and amplification of viruses. Using this BES, we expressed a recombinant spider flagelliform protein in BmN cell line, which was around 37 kDa in sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and western blot analysis. The BmNPV bacmid system using silkworm would be very attractive for expression of target proteins.

Novel molecular and mechanical properties of egg case silk from wasp spider, Argiope bruennichi.

Araneoid spiders use specialized abdominal glands to produce up to seven different protein-based silks/glues that have various mechanical properties. To date, the fibroin sequences encoding egg case fibers have not been fully determined. To gain further understanding of a recently reported spider silk protein gene family, several novel strategies were utilized in this study to isolate two full-length cDNAs of egg case silk proteins, cylindrical silk protein 1 (CySp1, 9.1 kb) and cylindrical silk protein 2 (CySp2, 9.8 kb), from the wasp spider, Argiope bruennichi. Northern blotting analysis demonstrated that CySp1 and CySp2 are selectively expressed in the cylindrical glands. The amino acid composition of raw egg case silk was closely consistent with the deduced amino acid composition based on the sequences of CySp1 and CySp2, which supports the assertion that CySp1 and CySp2 represent two major components of egg case silk. CySp1 and CySp2 are primarily composed of remarkable homogeneous assemble repeats that are 180 residues in length and consist of several complex subrepeats, and they contain highly homologous C-termini and markedly different N-termini. Our results suggest a possible link between CySp1 and CySp2. In addition, comparisons of stress/strain curves for dragline and egg case silk from Argiope bruennichi showed obvious differences in ultimate strength and extensibility, and similarities in toughness.