collagen

what is the diameter of collagen fibrils?

50-200nm

What are the dimensions of fibrils?

50nm in diameter and several micrometers long. These are packed side by side in parallel bundles, called collagen fibers, in tendons.

How many AA does one collagen I alpha chain contain?

1050 AA

Alport syndrome

Can be passed on genetically, usually as X-linked dominant, but also as both an autosomal dominant and autosomal recessive disorder, sufferers have problems with their kidneys and eyes, loss of hearing can also develop in during the childhood or adolescent years

Knobloch syndrome

Caused by a mutation in the COL18A1 gene that codes for the production of collagen XVIII. Patients present with protrusion of the brain tissue and degeneration of the retina, an individual who has family members suffering from the disorder are at an increased risk of developing it themselves as there is a hereditary link

Osteogenesis imperfecta

Caused by a mutation in type 1 collagen, dominant autosomal disorder, results in weak bones and irregular connective tissue, some cases can be mild while others can be lethal, mild cases have lowered levels of collagen type 1 while severe cases have structural defects in collagen

What is the most common cell that creates collagen?

Fibroblasts

what is hydroxylation?

Hydroxylation is a chemical process that introduces a hydroxyl group into an organic compound (converts a CH group into a COH group). it is an oxidative process In biochemistry, hydroxylation reactions are often facilitated by enzymes called hydroxylases. Hydroxylation converts lipophilic compounds into water-soluble (hydrophilic) products that are more readily excreted.

What three hydroxylation reactions are usually seen in proteins? what catalyzes them?

IN PROTEINS: The principal residue to be hydroxylated in proteins is proline. The hydroxylation occurs at the gamma-C atom, forming Hyp. In some cases, proline may be hydroxylated instead on its beta-C atom. Lysine may also be hydroxylated on its delta-C aton, forming hydroxylysine (Hyl) These three reactions are catalyzed by very large, multi-subunit enzymes prolyl 4-hydroxylase, prolyl 3-hydroxylase and lysyl 5-hydroxylase, respectively. These reactions require iron (as well as molecular oxygen and α-ketoglutarate) to carry out the oxidation, and use ascorbic acid (vitamin C) to return the iron to its oxidized state. Deprivation of ascorbate leads to deficiencies in proline hydroxylation, which leads to less stable collagen, which can manifest itself as the disease scurvy. Since citrus fruits are rich in vitamin C, British sailors were given limes to combat scurvy on long ocean voyages; hence, they were called "limeys".

How is type I collagen typically formed?

INSIDE THE CELL: 1) two types of alpha chains (alpha 1, 2) are formed during translantion on ribosomes on RER. These are known as preprocollagen. They have registration peptides on each end and a signal peptide. 2)polypeptide chains are released into the lumen of the RER 3)signal peptides are cleaved inside the RER and the chains are now known as pro-alpha chains. 4)hydroxylation of lysine and proline amino acids occurs inside the lumen. This process is dependent on ascorbic acid (vitamin C) as a cofactor 5)glycosylation of specific hydroxylysine residues occurs 6) triple alpha helical structure is formed inside the ER from 2 alpha-1 and 1 alpha-2 chain 7)Procollagen is shipped to the golgi apparatus, where it is packaged and secreted by exocytosis OUTSIDE THE CELL: 1) Registration peptides are cleeaved and tropocollagen is formed by procollagen peptidase 2) multiple tropocollagen molecules form collagen fibrils, via covalent cross-linking (aldol reaction) by lysyl oxidase which links hydroxylysine and lysine residues. Multiple collagen fibrils form into collagen fibers 3)Collagen may be attached to cell membranes via several types of protein, including fibronectin and integrin.

what is the main AA composition of collagen?

It is atypical for proteins, particularly with respect to its high hydroxyproline content. The most common motifs in the amino acid sequence of collagen are glycine-proline-X and glycine-X-hydrosyproline, where X is any amino acid other than glycine, proline or hydroxyproline. Proline or hydroxyproline constitute about 1/6 of the total sequence. With glycine accounting for the 1/3 of the sequence, this means approximately half of the collagen sequence is not glycine, proline or hydroxyproline.

Why is the high glycine content of collagen important?

It is important with respect to stabilization of the collagen helix as this allows the very close association of the collagen fibers within the molecule, facilitating hydrogen bonding and the formation of intermolecular cross-links. This kind of regular repetition and high glycine content is found in only a few other fibrous proteins, such as silk fibroin. Because glycine is the smallest amino acid with no side chain, it plays a unique role in fibrous structural proteins. In collagen, Gly is required at every third position because the assembly of the triple helix puts this residue at the interior (axis) of the helix, where there is no space for a larger side group than glycine's single hydrogen atom. For the same reason, the rings of the Pro and Hyp must point outward. These two amino acids help stabilize the triple helix—Hyp even more so than Pro; a lower concentration of them is required in animals such as fish, whose body temperatures are lower than most warm-blooded animals. Lower proline and hydroxyproline contents are characteristic of cold-water, but not warm-water fish; the latter tend to have similar proline and hydroxyproline contents to mammals.[13] The lower proline and hydroxproline contents of cold-water fish and other poikilotherm animals leads to their collagen having a lower thermal stability than mammalian collagen.[13] This lower thermal stability means that gelatin derived from fish collagen is not suitable for many food and industrial applications

Osteoporosis

Not inherited genetically, brought on with age, associated with reduced levels of collagen in the skin and bones, growth hormone injections are being researched as a possible treatment to counteract any loss of collagen.[34]

Ehlers-Danlos Syndrome

Six different types of this disorder, which lead to deformities in connective tissue. Some types can be lethal, leading to the rupture of arteries. Each syndrome is caused by a different mutation, for example type four of this disorder is caused by a mutation in collagen type 3

Chondrodysplasias

Skeletal disorder believed to be caused by a mutation in type 2 collagen, further research is being conducted to confirm this.[

What is the basal lamina?

The basal lamina is a layer of extracellular matrix secreted by the epithelial cells, on which the epithelium sits. It is often confused with the basement membrane and at times used inconsistently in literature. The basal lamina is visible only with the electron microscope, where it appears as an electron-dense layer, 20-100 nm thick (with exceptions such as the basal laminae that compose the 100-200 nm thick glomerular basement membrane

where does the word collagen come from?

The name collagen comes from the Greek κόλλα (kólla), meaning "glue", and suffix -γέν, -gen, denoting "producing".This refers to the compound's early use in the process of boiling the skin and sinews of horses and other animals to obtain glue

How are the 3 alpha chains linked together?

The side chain of glycine, an H atom, is the only one that can fit into the crowded center of a three-stranded helix. Hydrogen bonds linking the peptide bond NH of the glycine residue with peptide carbonyl (C=O) group in an adjacent polypeptide help hold the three chains together. The fixed angle of the C-N peptidyl-proline or peptidyl-hydroxyproline bond enables each polypeptide chain to fold into a helix with geometry such that three polypeptide chains can twist together to form a three-stranded helix. Interestingly, although the rigid peptidyl-proline linkages disrupt the packing of AA in an alpha helix, they stabilize the rigid three-stranded collagen helix.

What is the difference between the basal lamina vs. basement membrane

The term "basal lamina" is usually used with electron microscopy, while the term "basement membrane" is usually used with light microscopy.

Where is Type I Collagen found?

This is the most abundant collagen of the human body. It is present in scar tissue, tendons, skin, artery walls, cornea, the endomysium surrounding muscle fibers, fibrocartilage, and the organic part of bones and teeth. Over 90% of the collagen in the human body is type I.

Briefly, list the components that form a collagen fibre

Three polypeptides coild to form tropocollagen. Many tropocollagens then bind together to form a fibril, and many of these then form a fibre.

How does vitamin C deficiency affect collagen formation and what is this caused?

Vitamin C deficiency causes scurvy, a serious and painful disease in which defective collagen prevents the formation of strong connective tissue. Gums deteriorate and bleed, with loss of teeth; skin discolors, and wounds do not heal. Prior to the 18th century, this condition was notorious among long-duration military, particularly naval, expeditions during which participants were deprived of foods containing vitamin C

Do SC secrete collagen?

Yes (type IV procollagen, V)

basement membrane

can be seen with light microscope. composed of three layers (lamina lucida, lamina densa, and lamina fibroreticularis) which are visible under the electron microscope. The lamina densa is the basal lamina.

Collagen II

cartilage (main collagenous component of cartilage)

Collagen V

cell surfaces, hair and placenta

what is gelatin?

collagen that has been irreversibly hydrolyzed

What is the main structural protein in the extracellular space in connective tissue in animals? How abundant is this protein.

collagen. As the main component of connective tissue, it is the most abundant protein in mammals, making up from 25 to 35% of the whole-body protein content

Collagen IV

forms basal lamina, the epithelium-secreted layer of the basement membrane

what glycosylation occurs in collagen formation/

glycosylation of hydroxylysine residues. O-linked glycans are attached to the side-chains.

How strong is collagen I

gram for fram, type I collagen is stronger than steel

What is the difference between a left-handed helix and a right-handed alpha helix

https://www.quora.com/Why-are-most-alpha-helices-in-proteins-right-handed

what modifications occur to collagen in the ER?

hydroxylation, glycosylation and disulfide-bond formation

What is glycosylation?

it is the reaction in which a carbohydrate, i.e. a glycosyl donor, is attached to a hydroxyl or other functional group of another molecule (a glycosyl acceptor). in bioloby, glycosylation mainly referes in particular to the enzymatic process that attaches glycans to proteins, lipids, or other organic molecules. it is a form of co-translational and post-translational modification. Glycans serve a variety of structural and functional roles in membrane and secreted proteins. The majority of proteins synthesized in the rough ER undergo glycosylation. It is an enzyme-directed site-specific process, as opposed to the non-enzymatic chemical reaction of glycation. Glycosylation is also present in the cytoplasm and nucleus.

what is a single collagen molecule called and what are its dimensions?

known as tropocollagen; it is used to make up larger collagen aggregates, such as fibrils. It is approx. 300nm long and 1.5 nm in diameter, and it is made up of three polypeptide strands (called aplha peptides), each of which has the conformation of a left-handed helix. These three left-handed helices are twisted together into a right-handed triple helix or "super helix", a cooperative quaternary structure stabilized by many hydrogen bonds.With type I collagen and possibly all fibrillar collagens, if not all collagens, each triple-helix associates into a right-handed super-super-coil referred to as the collagen microfibril. Each microfibril is interdigitated with its neighboring microfibrils to a degree that might suggest they are individually unstable, although within collagen fibrils, they are so well ordered as to be crystalline

what autoimmune diseases may hurt collagen fibers?

lupus erythematosus or rheumatoid arthritis[18] may attack healthy collagen fibers

Collagen III

reticulate (main component of reticular fibers), commonly found alongside type I

How are fibrils formed? what are important in their formation?

short segments at either end of the collagen chains are important for formation of fibrils. these segments do not assume the triple-helical conformation and contain the unusual amino acid hydroxylysine. covalent aldol cross-links form between two lysine or hydroxylysine residues at the c-terminus of one collagen molecule with two similar residues at the N-terminus of an adjacent molecule. these cross-links stabilize the side-by-side packing of collagen molecules and generate a strong fibril.

Collagen I

skin, tendon, vascular ligature, organs, bone (main component of the organic part of bone)

How many types of collagen are there?

so far 28 types have been identified and described. The main ones that we discuss are fibrillar (type I, II, III, V, XI)

How do the tropocollagen subunits assemble?

spontaneously self-assemble,with regularly staggered ends, into even larger arrays in the extracellular spaces of tissues. n the fibrillar collagens, the molecules are staggered from each other by about 67 nm (a unit that is referred to as 'D' and changes depending upon the hydration state of the aggregate). Each D-period contains four plus a fraction collagen molecules, because 300 nm divided by 67 nm does not give an integer (the length of the collagen molecule divided by the stagger distance D). Therefore, in each D-period repeat of the microfibril, there is a part containing five molecules in cross-section, called the "overlap", and a part containing only four molecules, called the "gap".[21] The triple-helices are also arranged in a hexagonal or quasihexagonal array in cross-section, in both the gap and overlap regions

What does collagen do?

supports most tissues and gives cells structure from the outside; has great tensile strength; responsible for skin strength and elasticity and its degradation leads to wrinkles; strengthens blood vessels

Why does collagen form left handed rings?

the relatively high content of proline and hydroxyproline rings, with their geometrically constrained carboxyl and (secondary) amino groups, along with the rich abundance of glycine, accounts for the tendency of the individual polypeptide strands to form left-handed helices spontaneously, without any intrachain hydrogen bonding

What is the collagen structure?

triple helix, generally consisting of 2 identical (alpha 1) and an additional chain that differs slightly in its chemical composition (alpha 2)