Collagen: Difference between revisions
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<StructureSection load='4clg' size=' | <StructureSection load='4clg' size='350' side='right' caption='Structure of Collagen (PDB entry [[4clg]] or [[1cag]])' scene='Collagen/Opening/4' > | ||
==Overview== | ==Overview== | ||
'''Collagen''', the most abundant protein in vertebrates, is an extracellular, inextensible fibrous protein that comprises the major protein component of such stress-bearing structures as bones, tendons, and ligaments. As with all fibrous proteins collagen is, for the most part, characterized by highly repetitive simple sequence. Here we study two model compounds (The structure of [[4clg]]<ref>J.M. Chen, C.E. Kung, S.H. Feairheller, E.M. Brown, AN ENERGETIC EVALUATION OF A "SMITH" COLLAGEN MICROFIBRIL MODEL, <I>J. Protein Chem., </I>'''10''', 535, 1991</ref> is shown in the applet to the right.) for naturally occurring collagen, in order to develop an understanding of the fibrous portion of collagen and to show how the different levels of protein structure come together and form a highly ordered and stable fiber. Collagen's properties of rigidity and inextensibility are due to this highly ordered structure. The part of collagen without structural order is not illustrated in this model. This part of the protein complex having a different amino acid composition, lysine and hydroxylysine are particularly important residues, is globular in nature and not as structurally organized. Lysine and hydroxylysine form covalent crosslinks in the protein complex, thereby adding strength and some flexibility to the fiber. This covalent crosslinking continues throughout life and produces a more rigid collagen and brittle bones in older adults. Go to [[Collagen Structure & Function]] for information on the functions and disorders of collagen and a link in the External Links section of this page for assembly movies of the triple helix of types I and IV. | '''Collagen''', the most abundant protein in vertebrates, is an extracellular, inextensible fibrous protein that comprises the major protein component of such stress-bearing structures as bones, tendons, and ligaments. As with all fibrous proteins collagen is, for the most part, characterized by highly repetitive simple sequence. Here we study two model compounds (The structure of [[4clg]]<ref>J.M. Chen, C.E. Kung, S.H. Feairheller, E.M. Brown, AN ENERGETIC EVALUATION OF A "SMITH" COLLAGEN MICROFIBRIL MODEL, <I>J. Protein Chem., </I>'''10''', 535, 1991</ref> is shown in the applet to the right.) for naturally occurring collagen, in order to develop an understanding of the fibrous portion of collagen and to show how the different levels of protein structure come together and form a highly ordered and stable fiber. Collagen's properties of rigidity and inextensibility are due to this highly ordered structure. The part of collagen without structural order is not illustrated in this model. This part of the protein complex having a different amino acid composition, lysine and hydroxylysine are particularly important residues, is globular in nature and not as structurally organized. Lysine and hydroxylysine form covalent crosslinks in the protein complex, thereby adding strength and some flexibility to the fiber. This covalent crosslinking continues throughout life and produces a more rigid collagen and brittle bones in older adults. Go to [[Collagen Structure & Function]] for information on the functions and disorders of collagen and a link in the External Links section of this page for assembly movies of the triple helix of types I and IV. See also [[Fibrous Proteins]]. | ||
== Structure of a Segment == | == Structure of a Segment == | ||
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The <scene name='Collagen/1cag_surface/4'>surface</scene> of the tropocollagen is shown with the Ala appearing as olive and the Pro and Hyp adjacent to the Ala appearing as dark brown. Notice that the surface at these Pro and Hyp bulges slightly. This protrusion is due to the fact that the packing about the Ala side chains is not as close as it is about the Gly. In the two side-by-side scenes shown below compare the amount of open space between the chains in the area of the scene center. In the [[1cag]] scene in the area of the Ala the distance between the chains is slightly greater than that of [[4clg]] scene. | The <scene name='Collagen/1cag_surface/4'>surface</scene> of the tropocollagen is shown with the Ala appearing as olive and the Pro and Hyp adjacent to the Ala appearing as dark brown. Notice that the surface at these Pro and Hyp bulges slightly. This protrusion is due to the fact that the packing about the Ala side chains is not as close as it is about the Gly. In the two side-by-side scenes shown below compare the amount of open space between the chains in the area of the scene center. In the [[1cag]] scene in the area of the Ala the distance between the chains is slightly greater than that of [[4clg]] scene. | ||
==3D structures of collagen== | |||
[[Collagen 3D structures]] | |||
</StructureSection> | </StructureSection> | ||
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In order to convince yourself that there is a difference in the interchain distances in the area of the Ala, <scene name='Collagen/1cag_measurements/2'>show distances</scene> between Gly (Ala) and Pro which form intratropocollagen hydrogen bonds. Hydrogen bonds are not formed between Ala and Pro because the distances between the atoms forming the bonds are too great. The absence of the intratropocollagen hydrogen bonds, which is due to replacing Gly with a residue having a longer side chain, disrupts collagen's rope-like structure and is responsible for the symptoms of such human diseases as osteogenesis imperfecta and certain Ehlers-Danlos syndromes. | In order to convince yourself that there is a difference in the interchain distances in the area of the Ala, <scene name='Collagen/1cag_measurements/2'>show distances</scene> between Gly (Ala) and Pro which form intratropocollagen hydrogen bonds. Hydrogen bonds are not formed between Ala and Pro because the distances between the atoms forming the bonds are too great. The absence of the intratropocollagen hydrogen bonds, which is due to replacing Gly with a residue having a longer side chain, disrupts collagen's rope-like structure and is responsible for the symptoms of such human diseases as osteogenesis imperfecta and certain Ehlers-Danlos syndromes. | ||
==References== | ==References== | ||
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[[Category:Topic Page]] | [[Category:Topic Page]] | ||
[[pt:Collagen_(Portuguese)]] | |||