The primary structure of collagen.
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Amino Acid Sequence↗
Biomedical subjects
K Kühn
Publications and source records attributed to K Kühn.
Platelet-collagen interaction. The influence of native and modified collagen (Type I) on the aggregation of human platelets.
Type I collagen from calf skin, collagen modified by pepsin treatment, methylation, succinylation or deamidation, as well as the alpha-chains and cyanogen bromide peptides of the alpha1-chain were investigated with respect to their capacity to induce aggregation of human platelets. These preparations permitted an evaluation of the efficacy of the amino acid sequence, triple conformation,and various fibrillar structures in platelet aggregation. All collagens in dissolved in dissolved form (collagen dissolved at acid pH, pepsin-treated, methylated, deamidated, and succinylated collagen) induced platelet aggregation only after fibril formation. The arrangement of molecules within fibrils is of secondary importance. Modification of the side chains of amino acid residues affects primarily the formation of fibrils. The effect of these side chains on platelet aggregation is masked by the overwhelming potency of the fibrillar forms.
Amino Acid Sequence↗
[Early lesions of the human kidney in paraproteinemie an electron microscopic study (author's transl)].
INTRODUCTION: In paraproteinemia, especially in multiple myeloma, the origin and morphology of lesions in the kidneys still remain controversial. In many studies mostly of tissue obtained post mortem and examined with light microscopy, a discrepancy between impairment of renal function and minimal pathomorphological findings is often striking. The few studies done with the electron microscope up to now present a wide variety of morphological findings probably due to the different stages of kidney lesions examined, generally in patients with renal insufficiency and nephrotic syndrome. We have therefore tested the question whether early lesions are detectable in the nephron of patients with paraproteinemia who do not show any impairment of renal function. MATERIAL AND METHOD: Kidney biopsies were obtained from 8 patients with an average age of 58 years. 6 had multiple myeloma (3 IgG-, I IgA-, 2 Bence-Jones plasmacytoma), 1 Waldenström's disease and 1 an idiopathic paraproteinemia. Confirmation of the diagnoses was obtained by immunoelectrophoresis, bone marrow biopsy, and sternal puncture. In all cases creatinine clearance was normal and proteinuria was not increased substantially even in patients with a slight Bence-Jones-proteinuria. For electron microscopy small pieces from the renal biopsies were fixed in aldehydes followed by osmium tetroxide and embedded in Epon. The thin sections were stained with uranyl acetate followed by lead citrate...
Amyloid↗
[The polymorphism of collagen. New viewpoints on the structure and function of connective tissue].
Recent studies have established that connective tissue contains several chemically and genetically distinct collagens. Here we discuss the nature of these proteins, their occurrence in different tissues and their involvement in disease processes. Types I, II and II collagens show some similarities indicating a common origin. Morphological studies using antibodies against the various collagens indicate that the different collagens occur in different anatomical structures. Alterations in the distribution of these collagens are seen in tissues in certain disease states and may cause the loss of normal tissue function.
Age Factors↗
The fine structure of the kidney of the hagfish (Myxine glutinosa L.): A thin section and freeze-fracture study.
The fine structure of the kidney (glomerulus and archinephric duct) of the hagfish. Myxine glutinosa (L.) was studied in thin sections and by freeze-fracture technique. The glomerular filtration barrier is similar to that of mammalian kidneys. However, endothelial fenestrations are relatively scanty and the basement membranes of endothelial cells and podocytes always appear separated by a layer of collagen fibrils and microfibrils often surrounding numerous and extended mesangial cells. Between podocytes and their processes maculae occludentes and peculiar junctions of another type occur. The zonulae occludentes between epithelial cells of the archinephric duct are composed of five or more strands, occasionally of only one or two.
Animals↗
The covalent structure of collagen. The chymotrypsin, trypsin and hydroxylamine peptides derived from alpha2-CB4 of calf-skin collagen.
The cyanogen-bromide-derived peptide alpha2-CB4 from calf skin collagen, consisting of 321 amino acid residues, has been fragmented in order to obtain peptides suitable for automated sequential analysis. Digestion with chymotrypsin liberated six unique peptides consisting of 12, 17, 19, 54, 63 and 156 amino acid residues. Treatment of alpha2-CB4 with hydroxylamine yielded four peptides with 24, 87, 96 and 114 residues. No unspecific cleavage by hydroxylamine was encountered. All of the trypsin-derived peptides of alpha2-CB4 were isolated and characterized by their amino acid compositions. Most of the peptides isolated were ordered along the peptide chain of alpha2-CB4. Ordering of the peptides was greatly assisted by the isolation of double peptides from the chymotrypsin, trypsin and hydroxylamine-derived peptide mixtures.
Amino Acid Sequence↗
Immunohistochemical evidence for the presence of collagen type III in human arterial walls, arterial thrombi, and in leukocytes, incubated with collagen in vitro.
Sections of arterial walls and of thrombi and smears of leukocytes previously incubated in vitro with collagen type III were examined by immunohistochemical technique for the presence of collagen types I, II and III. In arterial walls collagen type III was detected immediately underlaying the endothelial cell layer and in the tissue between tunica elastica interna and adventitia. Collagen type I was not shown in the subendothelial layer. Fresh thrombi contained occasionally collagen, but only of type III. This was associated with leukocytes. Leukocytes were capable in vitro to associate and/or phagocytose collagen type III and this could be visualized immunohistochemically. The data show that collagen type III in vivo may play a crucial role in the initiation of thrombus formation.
Amino Acid Sequence↗
Comparative investigation on the influence of human and bovine collagen types I, II and III on the aggregation of human platelets.
Collagen types I, II and III from man and calf are distinctly different with respect to their effect on the induction of the aggregation of human platelets. Collagen type III was found to be a particularly potent inducer of platelet aggregation. The pathogenetic implications of these observations are briefly discussed.
Amino Acid Sequence↗
Information contained in the amino acid sequence of the alpha1(I)-chain of collagen and its consequences upon the formation of the triple helix, of fibrils and crosslinks.
The molecule of type I collagen from skin consists of two alpha1(I)-chains and one alpha2-chain. The sequence of the entire alpha1-chain comprising 1052 residues is summarily presented and discussed. Apart from the 279 residues of alpha1(I)-CB8 whose sequence has been established for rat skin collagen, all sequences have been determined for calf skin collagen. In order to facilitate sequence analysis, the alpha1-chain was cleaved into defined fragments by cyanogen bromide or hydroxylamine or limited collagenase digestion. Most of the sequence was established by automated stepwise Edman degradation. The alpha1-chain contains two basically different types of sequences: the triple helical region of 1011 amino acid residues in which every third position is occupied by glycine and the N- and C-terminal regions not displaying this type of regularity. Both of these non-triple helical regions carry oxidizable lysine or hydroxylysine residues as functional sites for the intermolecular crosslink formation. Implications of the amino acid sequence for the stability of the triple helix and the fibril as well as for formation of crosslinks are discussed. Evaluation of the sequence in connection with electron microscopical investigations yielded the parameters of the axial arrangement of the molecules within the fibrils. Axial stagger of the molecules by a distance D = 670 angstrom = 233 amino acid residues results in maximal interaction of polar sequence regions of adjacent molecules and similarly of regions of hydrophobic residues. Ordered aggregation of molecules into fibrils is, therefore, regulated by electrostatic and electrophobic forces. Possible loci of intermolecular crosslinks between the alpha1-chains of adjacent molecules may be deduced from the dimensions of the axial aggregation of molecules.
Amino Acid Sequence↗
The glomeruli of the human and the rat kidney studied by freeze-fracturing.
Glomeruli isolated from rat and human kidneys were studied using the freeze-fracture technique. Discontinuous zonulae occludentes and gap junctions were found in the replicas of the split plasma membrane of the endothelial cells. A diaphragm across the endothelial pores was not demonstrated. The central layer of the basement membrane, corresponding to the lamina densa described in thin sections, revealed a coarse substructure. A slit membrane between the pedicles of the podocytes was not detectable; however, its position was indicated by the different texture of the replica, which abruptly changed at the transition of the basement membrane to the primary urinary space. Furthermore, at the level of the slit membrane arrays of particles were present within the cleaved membrane of the pedicles, probably representing the attachment points of the slit membrane. Isolated strands of a zonula occludens as well as gap junctions were seen on the split plasma membrane of the podocytes. The mesangial cells could be identified by their contiguity to the endothelial cells and by their numerous gap junctions.
Adult↗
Junctional complexes of the tubular cells in the human kidney as revealed with freeze-fracture.
Intercellular junctions between human kidney tubular cells were studied by the freeze-fracture technique. The number of strands of the zonulae occludentes increased gradually from the proximal segment to the collecting tubule. Only one strand was visible in the proximal segment (in contrast to 2-4 strands of the neighbouring Bowman's capsule). In the thin segment 2-4 strands were revealed. In the distal segment 1-5 strands were present in the pars recta, 4-6 in the pars convoluta. The most extensive and complex zonulae occludentes were found in the collecting tubule. Gap junctions were seen only between proximal tubular cells. The extent of the zonulae occludentes along the tubules in human kidneys is very similar to that observed in the kidney tubules of other mammals. The findings accord well with electrophysiological measurements and with the results of tracer studies on experimental animals.
Adult↗
The covalent structure of collagen: amino-acid sequence of the cyanogen-bromide peptides alpha1-CB2, alpha1-CB4 and alpha1-CB5 from calf-skin collagen.
The amino acid sequence of 120 residues in the N-terminal region of the alpha1-chain of calf skin collagen (comprising the cyanogen-bromide-derived peptides alpha1-CB2, alpha1-CB4 and alpha1-CB5) has been determined by automated Edman degradation. The lysyl residue in position 87 is completely hydroxylated, while those in positions 99 and 108 partially hydroxylated. Two substitutions are found with respect to the homologous region of the alpha1-chain from rat skin collagen. Positions 101 and 102 of calf skin collagen are occupied by Asp-Ala, in rat skin collagen by Asn-Thr. The extensive homology in this region is remarkable and is not found in other regions of the alpha1 and alpha2-chain.
Amino Acid Sequence↗
Liver cirrhosis: immunofluorescence and biochemical studies demonstrate two types of collagen.
Pepsin solubilization of small and large noduled liver cirrhosis yielded two types of collagen (precipitated at 1.7 and 2.5 M NaCl concentrations) as demonstrated by electronmicroscopy. The 1.7 M NaCl precipitate was identified as type III collagen using an immunofluorescence technique. The 2.5 M NaCl precipitate appeared to be type I in the electronmicroscope. However, immunofluorescent and biochemical studies indicated that it was not type I but a type of collagen not yet described.
Aged↗
Comparative electron-microscope studies on type-III and type-I collagens.
Long-spacing-segment crystallites prepared from type III collagen with the chain composition [alpha1(III)]3 and type I collagen with the chain composition [alpha(I)]i12alpha2 have been compared in the electron microscope after positive. staining with phosphotungstic acid and uranyl acetate. The comparison revealed several differences in intensities of the cross-striation bands as well as significant differences in band positions. The latter occur most prominently in three distinct regions of the crystallites. Further, crystallites prepared from type III collagen contain an additional intensely staining band in an area corresponding to the carboxy-terminal end of the molecule. The latter band is still observed following limited pepsin digestion and presumably represents a slight elongation of the helical portion of the type III molecule when compared to the type I molecule. In spite of the somewhat altered distribution of charged groups as indicated in studies on the long-spacing-segment crystallites, type III molecules are capable of forming fibrils of the native type with a cross-striation pattern and periodicity virtually identical to that observed when type I molecules are precipitated as native fibers.
Amino Acid Sequence↗
[Stimulating effect of collagen and collagen derivatives on the propregation and adhesion of thrombocytes in defibrinogenated human citrate plasma and in animal citrate plasma].
Collagen type I form calf skin, collagen modified by pepsin, methylation, succinylation or deamidation and alpha1-chains or cyanogen bromide peptides were studied for their effect on adhesion and spreading of platelets. Some of the proteins increased platelet activity and indicated that the following structural parameters are of importance: 1. triple-helical conformation, 2. non-triple-helical regions, 3. charged amino acid side chains, 4. some activity was also detected for cyanogen bromide peptides of collagen alpha1-chain. The activity of collagen when used in a firbrinogen-free system is comparable to that of fibrinogen and potentiates platelet spreading caused by animal plasma.
Afibrinogenemia↗
The fine structure of the glomeruli as revealed by freeze-fracturing.
Isolated glomeruli of the rat kidney were investigated using the freeze-fracture method. The observations were consistent with those made on thin sections. Only exceptionally components of zonulae occludentes were seen between the capillary endothelial cells. The split membrane of mesangial cells revealed aspects of gap junctions.
Animals↗
Early lesions of the nephron in paraproteinemia.
Electron microscopy of renal biopsies in eight patients with paraproteinemia (six multiple myeloma, one Waldenström's disease, one idiopathic paraproteinemia) and without impairment of renal function demonstrates an increase of mesangial matrix and thickening of the lamina rara interna of the basement membrane in the glomerulus by fibrillar material without periodicity. These lesions are thought to exhibit precursors of amyloid deposits. The proximal tubules show signs of increased cellular activity probably because of handling an increased protein load. In the basement membranes there are proteins with a fibrillar structure and definite periodicity. These are suggested to be consistent with large aggregates of immunoglobulin fragments.
Humans↗
Isolation, chemical and electron microscopical characterization of neutral-salt-soluble type III collagen and procollagen from fetal bovine skin.
Extraction of fetal bovine skin at neutral pH and in the presence of protease inhibitors solubilized substantial amounts of type I and type type III collagen and Type III procollagen. Type I and Type III collagen were separated from each other by salt precipitation, and DEAE-cellulose chromatography was used to separate collagen from procollagen. The main chain constituents in type III collagen and procollagen were disulfide-bonded gamma and pgamma components, respectively. Amino acid composition, cross striation banding as observed using electron microscopy, cyanogen bromide peptide patterns in disc electrophoresis gels and resistance of the disulfide regions to pepsin digestion indicated a close similarity to previously described insoluble type III collagen, which was solubilized by limited pepsin digestion. Electron microscopy of long-spacing-segment crystallites and evidence for an extended form of the disulfide-bonded cyanogen bromide peptide suggested that neutral-salt-soluble type III collagon is longer at its C-terminal end by about 10 to 20 amino acid residues than pepsin-treated material. A small elongation was also indicated in the N-terminal portion of the molecule. Procollagen has an additional N-terminal extension with a length of about 160 A, but no difference was observed between collagen and procollagen at their C-terminal ends.
Amino Acids↗