Thermal instability of the trimeric structure of the N-terminal propeptide of human procollagen type I in relation to assay technology.
The N-terminal propeptide of procollagen type I (PINP) appeared in two peaks after size chromatography. The high-molecular weight form was transformed to the low-molecular weight form during incubation at 37 degreesC, whereas the low-molecular weight form remained unchanged. The PINP concentrations in amniotic fluid and sera remained unchanged during 37 degreesC incubation when measured using an ELISA; however, concentrations decreased by 89-93% when measured using an RIA. The ELISA:RIA ratio varied from 1.1 to 2.9 in these fluids because of different size distributions and the inability of the RIA to measure the low-molecular weight form. Thermal transition of the high-molecular weight form caused a change in its elution volume but did not change its migration in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Mass spectrometry revealed identical results for both forms. We reached the following conclusions: (a) the trimeric structure of PINP is unstable at 37 degreesC; (b) the two molecular forms represent intact alpha1 chains in trimeric and monomeric forms; (c) thermal transition is an ongoing in vivo process; and (d) this is important in the choice of assay technology.
Brandt
J
J
Department of Medical Microbiology, University of Odense, Denmark.
Krogh
T N
TN
Jensen
C H
CH
Frederiksen
J K
JK
Teisner
B
B
D000653:Amniotic Fluid / Q000737:chemistry; D002648:Child; D004591:Electrophoresis, Polyacrylamide Gel; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006358:Hot Temperature; D006801:Humans; D007122:Immunoelectrophoresis; D013058:Mass Spectrometry; D008970:Molecular Weight; D010446:Peptide Fragments / Q000097:blood / Q000737:chemistry*; D011247:Pregnancy; D011347:Procollagen / Q000097:blood / Q000737:chemistry*; D011487:Protein Conformation; D011863:Radioimmunoassay
D010446:Peptide Fragments; D011347:Procollagen