1

Chapter 13

Sequence Alterations in the Carboxyl-Terminal Propeptide Domain

Copyright © 2014 Elsevier Inc. All rights reserved.

2Copyright © 2014 Elsevier Inc. All rights reserved.

FIGURE 13.1 Biochemical collagen analysis of the secreted type I and III collagen proteins. (A) An abnormal migration pattern for type I collagen is observed for a patient (OI type IV) harboring the p.(Ala1286Arg) mutation in exon 50 of the COL1A1 gene. The mutation causes severe overmodifi cation of the α1(I) collagen chain, whilethe α2(I) collagen chain migrates slightly higher through gel. (B) A slightly decreased intensity for the type I collagen bands is detected for a patient (OI type I) carrying the p.(Cys1299*) in exon 50 of the COL1A1gene. (C) For a patient (OI type I) harboring the p.(Pro1182Arg) in exon 50 of the COL1A2 gene a near normal electrophoretic pattern for type I collagen is observed. (D) A patient (OI type I), carrying the p.(Trp1347*)mutation in exon 52 of the COL1A2 gene shows a broadened band representing the α1(I) chain; which is decreased in intensity. In addition, the α2(I) band has an increased mobility, an observation that has been documented in other COL1A2 C-propeptide mutations. 63 This fi gure is reproduced in color in the color plate section.

3Copyright © 2014 Elsevier Inc. All rights reserved.

FIGURE 13.2 Positions of known missense mutations in the C-propeptides of fi brillar procollagens I, II, III and V, mapped onto the structure of the pro-α1(III) C-propeptide. One chain of the pro-α1(III) C-propeptide trimer is shown in wheat, with the other chains shown (in part) in light gray. Numbering starts from the BMP1 cleavage site, according to the corresponding positions in the procollagen type III C-propeptide. Only mutation sites where the corresponding residues in the pro-α1(III) chains are identical are shown. Sites associated with lethal or severe forms of OI or skeletal dysplasias are in red and dark red, respectively, and those associated with mild or moderate forms in blue (OI) and dark blue (skeletal dysplasias). Asp222 isin purple, as two different mutations at the corresponding residue in pro-α1(I) lead either to mild [p.(Asp1441His)] 68 or lethal [p.(Asp1441Tyr)] 57 OI. Mutation sites in pro-α1(III) and pro-α1(V) are in green and dark green, respectively. Sites are numbered from the start of the C-propeptide domain.This fi gure is reproduced in color in the color plate section. (Drawn by using PyMOL, Version 1.4.1, Schrödinger, LLC; reprinted from 8 , with permission.)

4Copyright © 2014 Elsevier Inc. All rights reserved.

FIGURE 13.3 Alignment of the pro-α1(I), pro-α2(I), pro-α1(II), pro-α1(III) and pro-α1(V) C-propeptides showing the locations of all reported naturally occurring missense mutations (green boxes; see Table 13.1 for the COL1A1 mutations and Table 13.2 for the COL1A2 mutations). Different regions and secondary structure elements found in the procollagen III C-propeptide are also indicated, as are predicted secondary structures (obtained using PsiPred53) for the other C-propeptides. Also shown are the positions of Cys residues (numbered according to the sequence and also as Cys 1 to 8) with intrachain disulfi de bonds identifi ed as color-matched pairs. Residues involved in Ca2+ coordination are indicated by ● and the single N-linked glycosylation site by * (note Asn146 was mutated to Gln in the structure presented here). The long (12 residue) and short (3 residue) stretches of the discontinuous 15 residue chain recognition sequence are highlighted in wheat and deepteal color, respectively. Numbering refers to the C-propeptides of the pro-α1(III) chain. Sequence alignments and rendering were done using CLUSTALW34 and ESPript35, respectively. This fi gure is reproduced in color in the color plate section. (Reprinted from 8 , with permission.)