Studies on the sulfhydryl groups in type III collagen

Area of Science:

• Biochemistry
• Molecular Biology
• Structural Biology

Background:

• Type III collagen is a major fibrillar collagen.
• The molecule is a trimer of three alphal(III) chains.
• Each chain contains two cysteinyl residues, totaling six per molecule.

Purpose of the Study:

• To investigate the reactivity of sulfhydryl groups in Type III collagen.
• To determine the involvement of cysteinyl residues in collagen structure.
• To elucidate the bonding state of sulfhydryl groups in the native molecule.

Main Methods:

• Denaturation of Type III collagen.
• Assay for free sulfhydryl groups using alkylating reagents (iodo-[14C]acetic acid, 4-vinylpyridine).
• Analysis of potential disulfide-bonding with noncollagenous peptides.

Main Results:

• No free sulfhydryl groups were detected in denatured Type III collagen.
• Failure to form derivatives with iodo-[14C]acetic acid and 4-vinylpyridine.
• Absence of reactivity was not due to disulfide-binding with noncollagenous peptides.

Conclusions:

• All six sulfhydryl groups in Type III collagen participate in interchain disulfide-bonding.
• This extensive disulfide-bonding contributes to the structural integrity of the collagen molecule.
• The findings clarify the structural role of cysteinyl residues in Type III collagen.