Defective folding and stable association with protein disulfide isomerase/prolyl hydroxylase of type I procollagen with a deletion in the pro alpha 2(I) chain that preserves the Gly-X-Y repeat pattern.
We have studied the folding, processing, and association with two endoplasmic reticulum (ER) resident proteins of the abnormal type I procollagen molecules produced by a strain of fibroblasts harboring a 4.5 kilobase deletion in an allele of COL1A2 (Willing, M. C., Cohn, D.H., Starman, B. Holbrook, K.A., Greenberg, C.R., and Byers, P.H. (1988) J. Biol. Chem. 263, 8398-8404). By sequencing cDNA, we found that the mutant allele encodes pro alpha 2(I) chains that are shortened by 180 amino acids but retain the Gly-X-Y repeat pattern crucial for collagen triple helix formation. The type I procollagen molecules that incorporated the shortened chain were retained intracellularly and were stable. The triple helical domain in these molecules did not attain a normal conformation and remained accessible to posttranslational modifying enzymes amino-terminal to the deletion site for a prolonged period. The abnormal molecules folded into a triple helical conformation more slowly than the normal molecules, and the amino-terminal ends of the pro alpha 1(I) chains failed to become protease-resistant. While the abnormal procollagen molecules were not bound by the ER-resident protein BiP, they stably associated with protein disulfide isomerase, the beta-subunit of prolyl-4-hydroxylase. These results indicate that some mutations in type I collagen genes both transiently delay folding and permanently disrupt the structure of the triple helix and suggest that binding to prolyl-4-hydroxylase helps to retain certain abnormal procollagen molecules within the ER.
Chessler
S D
SD
Department of Pathology, University of Washington, Seattle 98195.
Byers
P H
PH
D000328:Adult; D000595:Amino Acid Sequence; D001483:Base Sequence; D002872:Chromosome Deletion; D003488:Cyanogen Bromide; D004247:DNA / Q000235:genetics; D016521:Electrophoresis, Gel, Pulsed-Field; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D006801:Humans; D007223:Infant; D007535:Isomerases / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D010449:Peptide Mapping; D011347:Procollagen / Q000235:genetics* / Q000378:metabolism; D011393:Procollagen-Proline Dioxygenase / Q000235:genetics* / Q000378:metabolism; D011487:Protein Conformation; D019704:Protein Disulfide-Isomerases; D011499:Protein Processing, Post-Translational; D012091:Repetitive Sequences, Nucleic Acid
D011347:Procollagen; D004247:DNA; D011393:Procollagen-Proline Dioxygenase; D007535:Isomerases; D019704:Protein Disulfide-Isomerases; D003488:Cyanogen Bromide