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Purification of human procollagen type I carboxyl-terminal propeptide cleaved as in vivo from procollagen and used to calibrate a radioimmunoassay of the propeptide.

We purified human procollagen type I carboxyl-terminal propeptide (PICP) that had been cleaved as in vivo from procollagen. PICP in serum-free medium from cultured human fetal fibroblasts was purified by thiophilic adsorption chromatography, low-pressure gel filtration, and HPLC gel filtration. The purity and homogeneity of the protein was verified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Amino-terminal amino acid sequencing showed that the sequences of the alpha 1 and alpha 2 chains of this PICP were identical to those of the PICP produced in vivo. The monocomponent PICP thus purified was used as calibrator in a simple equilibrium-type RIA of PICP with polyclonal antibodies raised in rabbits. The measuring range is 0.15-3.75 nmol/L, and the assay detection limit is 0.03 nmol/L. The within-run and total CVs are 2% and 4%, respectively. The reference interval for the plasma concentration of PICP in healthy women of ages > 30 years is 0.36-1.44 nmol/L (geometric mean 0.72 nmol/L, n = 154).

Adult↗

Serum concentrations of carboxyl-terminal propeptide of type I procollagen, amino-terminal propeptide of type III procollagen, cross-linked carboxyl-terminal telopeptide of type I collagen, and their interrelationships in schoolchildren.

We report pediatric age- and sex-specific 95% reference intervals for procollagen type I C-terminal propeptide (PICP), the cross-linked C-terminal telopeptide of type I collagen (ICTP), and procollagen type III N-terminal propeptide (P3NP), measured in plasma from 302 schoolchildren (156 boys, 146 girls) ages 4-19 years. All three markers displayed a significant variation with age (ANOVA P < or = 0.0015). PICP showed no detectable increase during adolescence for either sex, but decreased towards adult concentrations after the age of puberty, with an earlier decrease for girls than for boys (P < 0.01). ICTP and P3NP both increased in pubertal-aged children (P < 0.05), with an earlier increase in girls than in boys (P < 0.05), before decreasing towards adult concentrations (P < 0.01). All three collagen markers were highly correlated with one another (P < 0.001). The patterns observed mirrored the childhood growth curve and reflected the high turnover of bone and soft tissue during childhood growth.

Adolescent↗

Surface located procollagen N-propeptides on dermatosparactic collagen fibrils are not cleaved by procollagen N-proteinase and do not inhibit binding of decorin to the fibril surface.

Dermatosparaxis is a recessive disorder of animals (including man) which is caused by mutations in the gene for the enzyme procollagen N-proteinase and is characterised by extreme skin fragility. Partial loss of enzyme activity results in accumulation of pNcollagen (collagen with N-propeptides) and abnormal collagen fibrils in the fragile skin. How the N-propeptides persist in the tissue and how abnormal fibril morphology results in fragile skin is poorly understood. Using biochemical and quantitative mass mapping electron microscopy we showed that the collagen fibrils in the skin of a dermatosparactic calf contained 57% type I pNcollagen and 43% type I collagen and the fibrils were irregularly arranged in bundles and hieroglyphic in cross-section. Image analysis of the fibril cross-sections suggested that the deviation from circularity of dermatosparactic fibrils was caused by N-propeptides of pNcollagen being located at the fibril surface. Comparison of experimental and theoretical axial mass distributions of the fibrils showed that the N-propeptides were located to the overlap zone of the fibril D-period (where D=67 nm, the characteristic axial periodicity of collagen fibrils). Treatment of the dermatosparactic fibrils with N-proteinase did not remove the N-propeptides from the fibrils, although the N-propeptides were efficiently removed by trypsin and chymotrypsin. However, the N-propeptides were efficiently cleaved by the N-proteinase when the pNcollagen molecules were extracted from the fibrils. These results are consistent with close packing of N-propeptides at the fibril surface which prevented cleavage by the N-proteinase. Long-range axial mass determination along the fibril length showed gross non-uniformity with multiple mass bulges. Of note is the skin fragility in dermatosparaxis, and also the appearance of mass bulges along the fibril long axis symptomatic of the fragile skin of mice which lack decorin. Western blot analysis showed that the dermatosparactic fibrils bound elevated levels of the proteoglycan, compared with normal skin fibrils. The results showed that N-propeptides can distort the morphology of fibrils, that they do not inhibit binding of gap-associated macromolecules (such as decorin) and that the normal mechanical properties of skin are strongly dependent on the close association of near-cylindrical fibrils, thereby enabling maximal fibril-fibril interactions.

Animals↗

Catalysis by protein disulphide-isomerase of the assembly of trimeric procollagen from procollagen polypeptide chains.

Type-I procollagen, 14C-biosynthetically labelled, was reduced under denaturing and non-denaturing conditions. Reoxidation to disulphide-linked trimers occurred with non-denatured chains in the presence of an oxidant system containing oxidized and reduced glutathione. Dimeric intermediates were not detected. This reoxidation was accelerated by homogeneous beef liver protein disulphide-isomerase.

Animals↗

Immunohistochemical localization of procollagen types I and III during placentation in pregnant rats by type-specific procollagen antibodies.

To examine the sequential localizations of procollagen Types I (Pro I) and III (Pro III) during chorioallantoic placental formation in pregnant rats, we prepared polyclonal anti-rat Pro I- and III-specific antibodies. Biochemical analysis of a fraction containing [14C]-glycine-incorporated collagen from pregnant rat uteri showed that collagen Types I and III were actively synthesized during placental development. We examined 8-, 9.5-, 13-, and 20-day gestation rat uteri immunohistochemically. At Days 8 and 9.5, in the basal decidua facing the fetal cytotrophoblastic giant cell layer and implantation site, the immunoreactivity for Pro I was higher than that for Pro III. On Day 13, the enlarged myometrium and cytotrophoblastic cell layer showed increased immunoreactivity for Pro III. Unexpectedly, polygonal trophoblastic cells invading and modifying the maternal central artery showed intense immunoreactivity for Pro III. On Day 20, the fetal mesenchyme, large fetal blood vessels, and subendothelial stroma, including fetal blood capillaries, were more immunoreactive to Pro III antibody than to Pro I antibody in the labyrinth. Pro I and III synthesis and processing appear to be developmentally regulated and may be related to control of the microenvironment for supporting the fetus, control of the maternal blood supply stabilizing the fetoplacental physiological functions, and parturition.

Animals↗

Carbohydrate moieties of procollagen: incorporation of isotopically labeled mannose and glucosamine into propeptides of procollagen secreted by matrix-free chick embryo tendon cells.

Cells obtained from chick embryo tendons incorporate isotopically labeled glucosamine and mannose into the pro-alpha1 and pro-alpha2 chains of procollagen as judged by sodium dodecyl sulfate-gel filtration and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The label was further localized to the propeptides of pro-alpha1 and pro-alpha2 by its chromatographic behavior after digestion with bacterial collagenase or alpha-chymotrypsin. Carbohydrate analysis of isolated pro-alpha chains showed the presence of labeled galactosamine in addition to mannose and glucosamine. Resistance to mild alkaline hydrolysis suggested that greater than 90% of the oligosaccharide units are not linked to the propeptide backbone by either serine or threonine.

Animals↗

Is the aminoterminal propeptide of type III procollagen degraded in the liver? A study of type III procollagen peptide in serum during liver transplantation in pigs.

The aminoterminal propeptide of type III collagen was monitored in serum during liver transplantation in nine pigs. The aim was to investigate whether removal of the liver causes any changes in the serum concentration of the propeptide. Another connective tissue component, hyaluronan, a glycosaminoglycan known to be degraded in the liver endothelial cells, was also measured. Removal of the liver caused a significant increase in the concentration of the intact propeptide as well as of hyaluronan. Gel filtration confirmed the increase in the amount of intact propeptide. However, another large propeptide-related antigen, eluted near the void volume, appeared in the antigen profile during the anhepatic phase. This peak probably represents the propeptide still attached to the collagen molecule (pN collagen). The findings indicate that the liver is involved in the degradation of the propeptide and of larger propeptide-holding proteins.

Animals↗