The chemistry and structure of collagen

The possible role of neutrophil proteinases in damage to articular cartilage

The proteolytic degradation of articular cartilage that is seen in the arthritides affects both of the major structural components of the tissue, proteoglycan and collagen. Neutrophil leucocytes are abundant in the synovial fluid of the inflamed joints, and we have considered whether the large quantities of neutral proteinases carried by these cells could contribute to the cartilage degradation. The two neutrophil serine proteinases have been isolated, and shown to break down both proteoglycan and collagen in articular cartilage. The enzymes attacked the non-helical terminal peptides of the collagen, eliminating the cross-links, thus destabilizing and solubilizing, the fibres. The soluble collagen then denatured spontaneously, and was further degraded. Although large quantities of the neutrophil proteinases are probably released in the synovial fluid each day, the inhibitory capacity of the fluid is seldom, if ever, saturated. Nevertheless, immunologically mediated release of the neutrophil enzymes in 'frustrated endocytosis' at the cartilage surface could give rise to the generalized damage that has been reported by others.

Isolation and characterization of epithelial and connective tissue cells from rat palate

Epithelial and connective tissue cells were isolated from rat palate by sequential enzymatic digestion. Differences between the two populations were noted with respect to proline uptake and incorporation, % collagen synthesized, effects of parathyroid hormone and metabolism of D-valine. From these studies it can be concluded that the cell populations are viable and distinct with respect to the biochemical parameters examined.

Autoimmunity to type II collagen an experimental model of arthritis

We have found that intradermal injection of native type II collagen extracted from human, chick or rat cartilage induces an inflammatory arthritis in approximately 40% of rats of several strains whether complete Freund's adjuvant or incomplete Freund's adjuvant is used. Type I or III collagen extracted from skin, cartilage proteoglycans and alpha1(II) chains were incapable of eliciting arthritis, as was type II collagen injected without adjuvant. The disease is a chronic proliferative synovitis, resembling adjuvant arthritis in rats and rheumatoid arthritis in humans. Native type II co-lagen modified by limited pepsin digestion still produces arthritis, suggesting that type-specific determinants residing in the helical region of the molecule are responsible for the induction of disease. Since homologous type II collagen emulsified in oil without bacterial preparations regularly causes the disease, this new animal model of arthritis represents a unique example of experimentally-inducible autoimmunity to a tissue component.

Multistranded helix in xanthan polysaccharide

The extracellular polysaccharide xanthan is shown by electron microscopy to be an unbranched, probably double-stranded fiber 4 nanometers wide and 2 to 10 micrometers long when native. Denaturation yields a single strand only 2 nanometers wide and 0.3 to 1.8 micrometers long. Renatured xanthan shows short unraveled regions with two or three strands arranged in a right-handed twist.

The degradation of articular collagen by neutrophil proteinases

The action of the serine proteinase (EC 3.4.21--)of human neutrophil leucocytes, elastase and cathepsin G, on cartilage and tendon was investigated. With cartilage, both enzymes first degraded the proteoglycan, then solubilized collagen by an attack on the terminal peptides, destroying the inter- and intramolecular cross-links. There was little degradation of the helical region of the type II collagen. Elastase also solubilized type I collagen from tendon, though this was less susceptible than cartilage collagen, and attacked the terminal peptides and perhaps the helical region of type I skin collagen in solution. Cathepsin G had little or no effect on type I collagen of skin or tendon. Since massive infiltration of joint tissues by neutrophil leucocytes is a prominent feature of inflammatory joint disease, it may well be that elastase and cathepsin G make a significant contribution to the tissue damage that occurs.

Immune neutrality of calf skin collagen gel used to stimulate revitalization in pulpless open apex teeth of rhesus monkeys

A collagen mineral gel has recently been shown to stimulate revitalization of pulpless open apex teeth when syringed into debrided root canals. Experiments were conducted to examine possible stimulation of the immune system by the experimental procedure. Ring tests (interface precipitation analysis), Ouchterlony plates and hemagglutination tests on plasma samples taken from experimental rhesus monkeys throughout the healing process indicate a complete lack of humoral immune responsiveness to the injected collagen.

Localization of collagenase in human middle ear cholesteatoma

The process of connective tissue breakdown in chronic otitis media is described in the context of recent advances in our understanding of collagen degradation and bone resorption. The significance of the initial step in collagen breakdown, brought about by the action of a specific collagen dissolving enzyme is emphasized in terms of recent studies in other chronic inflammatory diseases characterized by connective tissue breakdown. Bone resorption, a characteristic feature of chronic otitis media, requires the breakdown of collagen, which comprises over 90 percent of bone protein. Evidence in support of collagenase in bone resorption from adjacent tissue (in this case, inflammatory connective tissue) would require identification of the enzyme in cells involved in the inflammatory process adjacent to the resorbing bone. Collagenase was found localized in frozen sections of canal wall skin, middle ear granulation and in cholesteatoma by a specific binding of the enzyme with an antiserum produced against purified human skin collagenase. The antigen antibody complex was labelled with fluorescein. Collagenase appeared in the subepithelial connective tissue of cholesteatoma, granulation tissue from the middle ear and the dermis of canal skin; but was not seen in the keratin layer, epithelium or the epidermal appendages. The enzyme appeared within certain fibroblasts, macrophages and endothelial cells of capillary buds. Collagenase enhanced by chronic inflammation attacks the intact collagen molecule, making it susceptible to further digestion by other proteases that are also products of inflammation. This process brings about resorption of connective tissue and bone.

Hydroxylation of (Pro-Pro-Gly)5 and (Pro-Pro-Gly)10 by prolyl hydroxylase. Evidence for an asymmetric active site in the enzyme

Previous studies with 14C-labeled synthetic peptides demonstrated that prolyl hydroxylase, which synthesizes the hydroxyproline in collagen, preferentially hydroxylates the fourth triplet from the NH-terminal end of the peptide (Pro-Pro-Gly)5. In the experiments reported here, the prolyl hydroxylase reaction was investigated further by preparing chemically modified derivatives of (Pro-Pro-Gly)5 and by synthesizing 14C-labeled preparations of (Pro-Pro-Gly)10. Essentially, the same kcat value was found for the hydroxylation of (Pro-Pro-Gly)5, N-acetyl-(Pro-Pro-Gly)5, (Pro-Pro-Gly)5 methyl ester, (Pro-Pro-Gly)10, and for larger polypeptide substrates of the enzyme. It appeared therefore that preferential hydroxylation of specific triplets in peptides of the structure (Pro-Pro-Gly)n cannot be explained by differences in the kinetic constants for individual triplets. Hydroxylation of 14C-labeled preparations of (Pro-Pro-Gly)10 demonstrated that the ninth triplet was preferentially hydroxylated over any other triplet. The results were best explained by the hypothesis that prolyl hydroxylase has an asymmetric active site in which binding subsites are located adjacent to but not symmetrical with the catalytic subsite.

Muscle actin filaments bind pituitary secretory granules in vitro

Hog anterior pituitary secretory granules sediment at 3,000 g. When rat or rabbit skeletal muscle actin filaments are present with the granules, the sedimentation decreases markedly. Depolymerized actin or viscous solutions of Ficoll and collagen have no effect on granule sedimentation. With this assay, actin filaments bind secretory granules (consisting of the proteinaceous core plus limiting membrane), secretory granule membranes, mitochondria, artificial lecithin liposomes, and styrene-butadiene microspheres, but have little or no interaction with membrane-free secretory granule cores and albumin microspheres. A secretory granule-actin complex sedimentable between 3,000 g and 25,000 g can be isolated. Metal ions, nucleotides, salts, dithiothreitol, or pretreatment of the granules with trypsin do not destroy the binding, which appears to be a lipophilic interaction.

Amino acid sequence of the N-terminal forty-two amino acid residues of the C chain of subcomponent C1q of the first component of human complement

1. The sequence of the N-terminal 42 amino acid residues and the identity of residue 45 of the C chain of subcomponent C1q were established by the use of the automatic protein sequencer. 2. A comparison of the amino acid sequences of the A and C chains of subcomponent C1q shows that they are identical at 18 positions out of the first 45. However, 12 of the amino acid residues in the positions of identity are glycine residues occurring in the repeating triplet sequence Gly-X-Y. 3. Position 36 in the C chain was found to be alanine, which was unexpected since the residue in this position would have to be glycine if the repeating triplet sequence Gly-X-Y were to extend, uniformly, throughout the entire length of the C-chain collagen-like region. This break in the repeating triplet sequence would prevent residue 36 in the C chain from taking part in collagen-like triple-helix formation. 4. The sequence information presented here therefore indicates that there should be a break, or distortion, located approximately half-way along each of the six collagen-like triple-helical regions proposed to be present in subcomponent C1q [Reid & Porter (1976) Biochem. J. 155, 19-23] and this is consistent with what is seen in electron micrographs of intact and pepsin-digested subcomponent C1q.

A murine tumor producing a matrix of basement membrane

We have studied a murine tumor previously classified as a poorly differentiated chondrosarcoma. Although the cells in this tumor are surrounded by large quantities of extracellular matrix material, the matrix fails to react with stains specific for the sulfated glycosaminoglycans present in normal cartilage. Here we show at the ultrastructural level that the tumor matrix is a homogeneous, nonfibrillar material, resembling basement membrane. Neither the proteoglycan matrix granules nor collagen fibrils characteristic of cartilage are present in the tumor matrix. Amino acid analyses of whole tumor tissue, enzyme-solubilized tumor components, and the protein extracted from lathyritic tumors confirmed that the tumor matrix is a basement membrane collagen. The collagenous protein extracted from the tumor by nonenzymatic means contains three unique polypeptides larger than the alpha-chain components of the other types of collagen. These studies indicate that the tumor is not a type of chondrosarcoma but a basement membrane producing tumor.

Improved technique for the analysis of amino acids and related compounds on thin layers of cellulose.XI. Direct, visual micro-method for investigating the primary structural sequence of collagen and other proteins

The present paper describes a new variation of the "finger printing" technique for examining the primary structure of proteins. It is based on the production of a reproducible, partial acid hydrolysate consisting of amino acids and small peptides which are separated into compact spots by bi-dimensional thin-layer chromatography. The spots are characterized by ther Rf values and colour reactions with a variety of reagents. The method was initially developed for collagen but has been applied to other proteins, with interesting results. It has developed logically from earlier, systematic studies on amino acids and peptides, and holds promise for the comparative investigation of normal and diseased human collagen.

Biochemical characteristics and biological significance of the genetically-distinct collagens

In recent years it has become evident that genetic polymorphism is dramatically expressed in the structural protein, collagen. Current information on the biochemical properties, biosynthesis, and tissue distribution of Type I, II, and III collagens is summarized with special reference to possible unique functional roles fulfilled by each of these collagens.

Isolation of a crosslinked cyanogen-bromide peptide from insoluble rabbit collagen. Tissue differences in hydroxylation and glycosylation of the crosslink

A radioactive peptide has been isolated from cyanogen bromide digests of sodium boro[3H]-hydride-reduced collagen from rabbit bone, tendon and skin. It was identified as a crosslinked peptide linking the short C-terminal cyanogen bromide peptide alpha1-CB6B (17 amino acid residues) to alpha1-CB5 (37 residues) from the helical part of the chain of an adjacent molecule. Both peptides could be separated after cleaving the crosslink with periodate. Thus the crosslinked peptide alpha1-CB5 X alpha1-CB6B originates from an intermolecular crosslink between quarter-staggered molecules within collagen fibrils previously assigned as 'head-to-tail' link. The chemical nature of the reduced crosslinking component was identified and was shown to differ between peptides derived from different tissues: alpha1-CB6B X alpha1 CB5 from bone contains hydroxylysinohydroxynorleucine [o5Lys(o5omegaNle)] whereas the skin peptide contains hydroxylysinonorleucine [o5Lys(omegaNle)]. The peptide derived from tendon contains both components. The relation of o5Lys(omegaNle) to o5Lys(o5omegaNle) in the peptides corresponds to that of the original tissue. On the other hand, histidino-hydroxymerodesmosine which is a major reduced cross-linking component in skin and tendon, is completely absent in the isolated peptides. The crosslinking component in the skin peptide is completely glycosylated, mainly by glucosylgalactosyl residues and to a smaller extent by galactosyl residues. o5Lys(o5omegaNle) from the bone peptide is only partly glycosylated, containing equal amounts of the disaccharide and monosaccharide. Only slight glycosylation was found in the tendon peptide.

Structure of psammoma bodies of a meningioma in scanning electron microscopy

Psammoma bodies in a human transitional meningioma were studied by scanning electron microscopy (SEM) of deparaffinized tissue slices and sections. The bodies, visible as round structures by light microscopy, were confirmed in SEM to have a spherical rather than tubular three-dimensional structure. They were distinctly demarcated from a surrounding cup-like wall of cells. Under high magnification, the undulating surface of the bodies was found to be covered by interwoven fibers. In cross-section the bodies had a lamellar internal structure. The lamellae consisted of a network of concentric strands and fibers with associated bead-like material. The structure of psammoma bodies seen in SEM speaks in favor of their genesis by calcification of concentrically deposited fibrillar extracellular material.

NH2-terminal extensions on skin collagen from sheep with a genetic defect in conversion of procollagen into collagen

A modified form of procollagen was extracted with 10 M urea from the skin of lambs with dermatosparaxis, a disease which is produced by a genetic defect in the conversion of procollagen to collagen. The extracts contained little if any alpha1 and alpha2 chains of normal type I collagen, and instead they contained the larger polypeptides palpha1 and palpha2 together with high polymers. palpha1 was purified by ion-exchange chromatography and gel filtration. The polypeptide was shown to be related to alpha1 by its chromatographic behavior, its amino acid composition, and the peptides obtained after cleavage with cyanogen bromide. The molecular weight of palpha1 by gel filtration was 112 300 +/- 6300. After digestion of palpha1 with bacterial collagenase, a fragment of about 100 amino acid residues was obtained which was similar in amino acid composition and antigenic activity to a comparable fragment previously obtained from the NH2-terminal region of palpha1 chains from dermatosparaxic cattle. However, after cleavage of palpha1 with cyanogen bromide, a larger NH2-terminal fragment of about 160 amino acid residues was obtained. The larger cyanogen bromide fragment contained 8 residues of hydroxyproline, 12 residues of proline, and 19 residues of glycine not found in the NH2-terminal fragment isolated after digestion with bacterial collagenase. The results indicated that, in addition to containing amino acid sequences similar to those found in globular proteins, the peptide extensions on the NH2-terminal end of the palpha1 chain of procollagen also contain amino acid sequences similar to those found in the triple-helical region of the collagen molecule. The molecular weight of palpha2 by gel filtration was 102 400 +/- 6800. No additional peptide fragment was recovered after digestion of palpha2 with bacterial collagenase.

Subunit composition and structure of subcomponent C1q of the first component of human complement

1. Unreduced human subcomponent C1q was shown by electrophoresis on polyacrylamide gels run in the presence of sodium dodecyl sulphate to be composed of two types of non-covalently linked subunits of apparent mol.wts. 69 000 and 54 000. The ratio of the two subunits was markedly affected by the ionic strength of the applied sample. At a low ionic strength of applied sample, which gave the optimum value for the 54 000-apparent mol.wt. subunit, a ratio of 1.99:1.00 was obtained for the ratio of the 69 000-apparent mol.wt. subunit to the 5400-apparent-mol.wt. subunit. The amount of the 54 000-apparent-mol.wt. subunit detected in the expected position on the gel was found to be inversely proportional to increases in the ionic strength of the applled sample. 2. Human subcomponent C1q on reduction and alkylation, or oxidation, yields equimolar amounts of three chains designated A, B and C [Reid et al. (1972) Biochem. J. 130, 749-763]. The results obtained by Yonemasu & Stroud [(1972) Immunochemistry 9, 545-554], which showed that the 69 000-apparent-mol.wt. subunit was a disulphide-linked dimer of the A and B chains and that the 54 000-apparent-mol.wt. subunit was a disulphide-linked dimer of the C chain, were confirmed. 3. Gel filtration on Sephadex G-200 in 6.0M-guanidinium chloride showed that both types of unreduced subunit were eluted together as a single symmetrical peak of apparent mol.wt. 49 000-50 000 when globular proteins were used as markers. The molecular weights of the oxidized or reduced A, B and C chains have been shown previously to be very similar all being in the range 23 000-24 000 [Reid et al. (1972) Biochem. J. 130, 749-763; Reid (1974) Biochem. J. 141, 189-203]. 4. It is proposed that subcomponent C1q (mol.wt. 410000) is composed of nine non-covalently linked subunits, i.e. six A-B dimers and three C-C dimers. 5. A structure for subcomponent C1q is proposed and is based on the assumption that the collagen-like regions of 78 residues in each of the A, B and C chains are combined to form a triple-helical structure of the same type as is found in collagens.