Structural protein

Tropocollagen triple helix

As structural proteins (also scleroproteins , fibrous proteins , ambiguous and scaffold proteins ) refers to proteins , which are primarily used as builders in tissues or cells of living things serve. In addition to globular proteins and membrane proteins , they form a main class of proteins.

properties

Structural proteins often have no catalytic function, i.e. they do not act as enzymes , but are among other things. a. significantly involved in the formation of fibers and cells giving their shape and tissues their strength and elasticity . Scleroproteins are used to mechanically stabilize tissues, e.g. B. in the cytoskeleton or in the extracellular matrix . Scleroproteins are often hydrophobic , have repeating amino acid sequences and form long fibers by aggregation of the monomers on hydrophobic surface areas. Structural proteins occasionally form unusual secondary structures due to the repeating units , e.g. As the collagen - triple helix . Occasionally the monomers of the structural proteins are cross-linked by disulfide bridges , e.g. B. Keratin . In the course of a protein design , parts of different structural proteins can be combined to form fusion proteins with modified skeletal properties.

Examples of structural proteins

Keratin of the hair , nails , hooves and horns of mammals , the feathers of birds and horn scales of reptiles .
Collagen of the connective tissue and the extracellular matrix of all tissue animals
Elastin
fibrillar (fibrous) structural proteins such as myosin and tropomyosin that cause muscle cells to contract ( motor proteins )
fibroin silk proteins from insects ( fibroin and sericin ) or spiders ( spidroin 1 and spidroin 2 )

Arthropodin and sclerotin (arthropodin tanned with phenol), next to chitin the main component of the body shell ( cuticle ) of the arthropods (arthropods)

Centrioles and microtubules of most living things

Microfilaments of the cytoskeleton of most living things

Structure characteristics

Most structural proteins are characterized by the fact that their amino acid sequence has regularly recurring clusters of amino acids . The consequence of this regular primary structure is a secondary structure arranged in longer areas (domains) , for example as a right-handed α-helix (in α-keratin) or as a narrow left-handed α-helix (in collagen ) or as a β-sheet (in β-keratin or in Fibroin of the insect silk) or as alternating crystalline and amorphous areas (in the fibroin of the spider silk).

Targeting

Structural proteins that are supposed to function outside of the cell have a signal sequence and are post-translationally indicated by specific glycosylation (targeting) that they should leave the cell by exocytosis .

Formation of covalent complexes

Structural proteins are often subject to post-translational modifications in order to form permanent (covalently bound) complexes with other molecules (e.g. collagen in collagen fibrils, fibroin in silk fibrils). This can happen outside the cell spontaneously (passively) or with the support of enzymes .

literature

Jan Koolman, Klaus-Heinrich Röhm: Pocket Atlas of Biochemistry. 3rd edition, Georg Thieme Verlag, 2003, ISBN 9783137594031 , pp. 70ff.

Web links

MeSH structural protein

Individual evidence

^ Ulrich Lehmann : Paleontological Dictionary . 4th edition. Ferdinand Enke Verlag, Stuttgart 1996, p. 100 .
↑ Berisio R, Vitagliano L, Mazzarella L, Zagari A: Crystal structure of the collagen triple helix model [(Pro-Pro-Gly) (10)] (3) . In: Protein Sci. . 11, No. 2, February 2002, pp. 262-70. doi : 10.1110 / ps.32602 . PMID 11790836 . PMC 2373432 (free full text).
↑ Bhattacharjee A, Bansal M: Collagen structure: the Madras triple helix and the current scenario . In: IUBMB Life . 57, No. 3, March 2005, pp. 161-72. doi : 10.1080 / 15216540500090710 . PMID 16036578 .
↑ Miroshnikov KA, Marusich EI, Cerritelli ME, et al. : Engineering trimeric fibrous proteins based on bacteriophage T4 adhesins . In: Protein Eng. . 11, No. 4, April 1998, pp. 329-32. doi : 10.1093 / protein / 11.4.329 . PMID 9680195 .

[PalWB-1] Ulrich Lehmann : Paleontological Dictionary . 4th edition. Ferdinand Enke Verlag, Stuttgart 1996, p. 100 .

[pmid11790836-2] Berisio R, Vitagliano L, Mazzarella L, Zagari A: Crystal structure of the collagen triple helix model [(Pro-Pro-Gly) (10)] (3) . In: Protein Sci. . 11, No. 2, February 2002, pp. 262-70. doi : 10.1110 / ps.32602 . PMID 11790836 . PMC 2373432 (free full text).

[3] Bhattacharjee A, Bansal M: Collagen structure: the Madras triple helix and the current scenario . In: IUBMB Life . 57, No. 3, March 2005, pp. 161-72. doi : 10.1080 / 15216540500090710 . PMID 16036578 .

[pmid9680195-4] Miroshnikov KA, Marusich EI, Cerritelli ME, et al. : Engineering trimeric fibrous proteins based on bacteriophage T4 adhesins . In: Protein Eng. . 11, No. 4, April 1998, pp. 329-32. doi : 10.1093 / protein / 11.4.329 . PMID 9680195 .