Summary Effectors of the innate immune system, the antibacterial peptides, have pivotal roles in preventing infection at epithelial surfaces. Here we show that proteinases of the significant human pathogens Pseudomonas aeruginosa , Enterococcus faecalis , Proteus mirabilis and Streptococcus pyogenes, degrade the antibacterial peptide LL-37. Analysis by mass spectrometry of fragments generated by P. aeruginosa elastase in vitro revealed that the initial cleavages occurred at Asn-Leu and Asp-Phe, followed by two breaks at Arg-Ile, thus inactivating the peptide. Proteinases of the other pathogens also degraded LL37 as determined by SDS-PAGE. Ex vivo , P. aeruginosa elastase induced LL-37 degradation in human wound fluid, leading to enhanced bacterial survival. The degradation was blocked by the metalloproteinase inhibitors GM6001 and 1, 10-phenantroline (both of which inhibited P. aeruginosa elastase, P. mirabilis proteinase, and E. faecalis gelatinase), or the inhibitor E64 (which inhibited S. pyogenes cysteine proteinase). Additional experiments demonstrated that dermatan sulphate and disaccharides of the structure [D UA(2S)-GalNAc(4,6S)], or sucroseoctasulphate, inhibited the degradation of LL-37. The results indicate that proteolytic degradation of LL-37 is a common virulence mechanism and that molecules which block this degradation could have therapeutic potential.

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Proteinases of common pathogenic bacteria degrade and inactivate the antibacterial peptide LL-37

Connective tissues maintain shape against external and internal stress. They are molecular hierarchies in which fundamental building units come together in tiers of increasing complexity and mutual interactions, based on information carried in the precursor molecules secreted by cells. The collagen fibril is the end product of well-understood self-aggregation controlled by its amino acid sequences, but the interfibrillar amorphous ground substance has not hitherto been seen as structured by analogous aggregations prescribed by the primary structures of the characteristic glycosaminoglycans dissolved therein. Transmission electron microscopy with morphometry and stereology has demonstrated their existence in tissues. Nuclear magnetic resonance defined their secondary structures, rotary shadowing electron microscopy delineated their aggregates in vitro, and molecular dynamics stimulations showed how the latter can spring from the former. The driving forces to aggregation are hydrophobic and hydrogen bonding...

Supramolecular organization of extracellular matrix glycosaminoglycans, in vitro and in the tissues.

Isolation of dermatan sulfate proteoglycans from mature bovine articular cartilages.

Connective tissues (CTs), which define bodily shape, must respond quickly, robustly and reversibly to deformations caused by internal and external stresses. Fibrillar (elastin, collagen) elasticity under tension depends on molecular and supramolecular mechanisms. A second intra-/inter-molecular pair, involving proteoglycans (PGs), is proposed to cope with compressive stresses. PG interfibrillar bridges (‘shape modules’), supramolecular structures ubiquitously distributed throughout CT extracellular matrices (ECMs), are examined for potential elastic properties. l-iduronate residues in shape module decoran PGs are suggested to be molecular springs, cycling through alternative conformations. On a larger scale, anionic glycosaminoglycan (AGAG) interfibrillar bridges in shape modules are postulated to take part in a sliding filament (dashpot-like) process, which converts local compressions into disseminated tensile strains. The elasticity of fibrils and AGAGs, manifest at molecular and larger-scale levels, provides a graduated and smooth response to stresses of varying degrees. NMR and rheo NMR, computer modelling, electron histochemical, biophysical and chemical morphological evidence for the proposals is reviewed.

Elasticity in extracellular matrix ‘shape modules’ of tendon, cartilage, etc. A sliding proteoglycan‐filament model

Structure of a Novel Oligosaccharide-Mycosporine-Amino Acid Ultraviolet A/B Sunscreen Pigment from the Terrestrial Cyanobacterium Nostoc commune

Interactions between dermatan sulpahte chains. III Light-scattering and viscometry studies of self-association☆

Connective tissue is composed of scattered cells embedded in an extracellular matrix consisting of abundant collagen fibers, elastin, and an amorphous ground substance dominated by proteoglycans. Proteoglycans contain a central protein core that is substituted with glycosaminoglycans. With the possible exception of hyaluronate all of the known glycosaminoglycans (Table 1) occur as proteoglycans. The various proteoglycans of the interfibrillar space are considered to control the architecture of the fibrillar network (Muir and Hardingham, 1975). A general observation is that the type of proteoglycan found in a tissue varies with the biomechanical properties of the tissue. The cartilage proteoglycan is especially designed for resisting compression and deformation by virtue of its aggregation with hyaluronate (carbohydrate—protein interaction) to form large, highly expanded supramolecular aggregates (Muir and Hardingham, 1975).

C. F. Phelps

Papers

Interactions between dermatan sulpahte chains. III Light-scattering and viscometry studies of self-association☆

Self-Association of Copolymeric Glycosaminoglycans (Proteoglycans)