Structural proteins

thumb|right|Sheet (or leaf) gelatin for cooking.

thumb|upright=1.5|The triple helix: three left-handed polyproline type II helices (red, green, blue) assemble by an axial hydrogen bond to form a right-handed triple helix, the tertiary structure of collagen.

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thumb|200x200px|Thick elastic fibers consisting of bundles of elastin in the human lung Elastin is a protein encoded by the ELN gene in humans and several other animals. Elastin is a key component in the extracellular matrix of gnathostomes (jawed vertebrates). It is highly elastic and present in connective tissue of the body to resume its shape after stretching or contracting. Elastin helps skin return to its original position whence poked or pinched. Elastin is also in important load-bearing tissue of vertebrates and used in places where storage of mechanical energy is required.

constitutes one of the three main types of proteins (alongside globular and membrane proteins). There are many scleroprotein superfamilies including keratin, collagen, elastin, and fibroin

thumb|Micrograph showing amyloid deposits (pink) in [[small bowel. Duodenum with amyloid deposition in lamina propria. Amyloid shows up as homogeneous pink material in lamina propria and around blood vessels. 20× magnification. ]] Amyloids are aggregates of proteins characterised by a fibrillar morphology of typically 7–13 nm in diameter, a β-sheet secondary structure (known as cross-β) and ability to be stained by particular dyes, such as Congo red. In the human body, amyloids have been linked to the development of various diseases. Pathogenic amyloids form when previously healthy proteins lo

thumb|Confocal microscopy|Confocal microscopic analysis of a [[dermal fibroblast in primary culture from a control (a and b) and the subject with HGPS (c and d). Labelling was performed with anti-lamin A/C antibodies. Note the presence of irregularly shaped nuclear envelopes in many of the subject's fibroblasts]] Lamins, also known as nuclear lamins, are fibrous proteins in type V intermediate filaments, providing structural function and transcriptional regulation in the cell nucleus. Nuclear lamins interact with inner nuclear membrane proteins to form the nuclear lamina on the interior of the

extracellular matrix part that consists of an insoluble core of polymerized tropoelastin monomers and a surrounding mantle of microfibrils

protein

Fibrillin is a glycoprotein, which is essential for the formation of elastic fibers found in connective tissue. Fibrillin is secreted into the extracellular matrix by fibroblasts and becomes incorporated into the insoluble microfibrils, which appear to provide a scaffold for deposition of elastin.

Filaggrin (filament aggregating protein; FLG) is a filament-associated protein that binds to keratin fibers in epithelial cells. Ten to twelve filaggrin units are post-translationally hydrolyzed from a large profilaggrin precursor protein during terminal differentiation of epidermal cells. In humans, profilaggrin is encoded by the FLG gene, which is part of the S100 fused-type protein (SFTP) family within the epidermal differentiation complex on chromosome 1q21. In cetaceans and sirenians, the FLG family has lost its function, with the curious exception of manatees in the latter clade: manatee

thumb|Crystal structure of Duck Delta 1 Crystallin, based on the Protein Data Bank|PDB file 1HY0. In anatomy, a crystallin is a water-soluble structural protein found in the lens and the cornea of the eye accounting for the transparency of the structure. It has also been identified in other places such as the heart, and in aggressive breast cancer tumors. The physical origins of eye lens transparency and its relationship to cataract are an active area of research. Since it has been shown that lens injury may promote nerve regeneration, crystallin has been an area of neural research. So far, it

thumb|300px Claudins are a family of proteins which, along with occludin, are the most important components of the tight junctions (zonulae occludentes). Tight junctions establish the paracellular barrier that controls the flow of molecules in the intercellular space between the cells of an epithelium. They have four transmembrane domains, with the N-terminus and the C-terminus in the cytoplasm.

thumb|Insect exoskeleton (comprising sclerotin): abandoned exuviae of a dragonfly

Coilin is a protein that in humans is encoded by the COIL gene. Coilin got its name from the coiled shape of the Cajal bodies in which it is found. It was first identified using human autoimmune serum.

aggregation of mis-folded proteins

Loricrin is a protein that in humans is encoded by the LOR gene.

inclusion bodies for misfolded proteins

InterPro Family

Extensins are a family of flexuous, rodlike, hydroxyproline-rich glycoproteins (HRGPs) of the plant cell wall.