Pneumococcal bacteriophage-encoded lysins are modular choline binding proteins that have been shown to act as enzymatic antimicrobial agents (enzybiotics) against streptococcal infections. Here we present the crystal structures of the free and choline bound states of the Cpl-1 lysin, encoded by the pneumococcal phage Cp-1. While the catalytic module displays an irregular (beta/alpha)(5)beta(3) barrel, the cell wall-anchoring module is formed by six similar choline binding repeats (ChBrs), arranged into two different structural regions: a left-handed superhelical domain configuring two choline binding sites, and a beta sheet domain that contributes in bringing together the whole structure. Crystallographic and site-directed mutagenesis studies allow us to propose a general catalytic mechanism for the whole glycoside hydrolase family 25. Our work provides the first complete structure of a member of the large family of choline binding proteins and reveals that ChBrs are versatile elements able to tune the evolution and specificity of the pneumococcal surface proteins.

Protein mechanostability is a fundamental biological property that can only be measured by single-molecule manipulation techniques. Such studies have unveiled a variety of highly mechanostable modules (mainly of the Ig-like, ␤-sandwich type) in modular proteins subjected to mechanical stress from the cytoskeleton and the metazoan cell-cell interface. Their mechanostability is often attributed to a ''mechanical clamp'' of secondary structure (a patch of backbone hydrogen bonds) fastening their ends. Here we investigate the nanomechanics of scaffoldins, an important family of scaffolding proteins that assembles a variety of cellulases into the so-called cellulosome, a microbial extracellular nanomachine for cellulose adhesion and degradation. These proteins anchor the microbial cell to cellulose substrates, which makes their connecting region likely to be subjected to mechanical stress. By using singlemolecule force spectroscopy based on atomic force microscopy, polyprotein engineering, and computer simulations, here we show that the cohesin I modules from the connecting region of cellulosome scaffoldins are the most robust mechanical proteins studied experimentally or predicted from the entire Protein Data Bank. The mechanostability of the cohesin modules studied correlates well with their mechanical kinetic stability but not with their thermal stability, and it is well predicted by computer simulations, even coarse-grained. This extraordinary mechanical stability is attributed to 2 mechanical clamps in tandem. Our findings provide the current upper limit of protein mechanostability and establish shear mechanical clamps as a general structural/functional motif widespread in proteins putatively subjected to mechanical stress. These data have important implications for the scaffoldin physiology and for protein design in biotechnology and nanotechnology.cellulosome ͉ cohesin ͉ mechanical stability ͉ protein nanomechanics ͉ single-molecule force spectroscopy

This paper describes the assembly of an updated quasi-global dataset of higher-frequency sea level information obtained from tide gauges operated by many agencies around the world. We believe that the construction of such a dataset is fundamental to scientific research in sea level variability and also to practical aspects of coastal engineering. A first version of the dataset was used in approximately a dozen published studies, and this second version is about twice the size, containing longer and more geographically representative sea level records. The dataset has acquired a digital object identifier and may be obtained from several sources. The paper mentions some of the merits of and deficiencies with the present version and takes a forward look at how the dataset may be updated in the future.

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A single-molecule study reveals that neurotoxic proteins share common structural features that may trigger neurodegeneration, thus identifying new targets for therapy and diagnosis.