Chain
The term chain, in biochemistry, usually denotes either a polypeptide chain or a polynucleotide chain. A polypeptide chain is a sequence of amino acids covalently linked by peptide bonds. A short polypeptide consisting of 50 or fewer amino acids is termed a peptide. A polynucleotide chain is a sequence of nucleotides covalently linked by ribose (or deoxyribose)-phosphate bonds, e.g. either DNA or RNA.
Polypeptide (protein) chains are linear, with rare exceptions where a side-chain forms a peptide bond[1][2]. Polypeptide chains may be covalently linked together, most commonly by disulfide bonds.
Protein molecules may consist of one or more polypeptide chains, homo-oligomers or hetero-oligomers, homo-multimers or hetero-multimers. The functional form of the molecule, termed the biological unit, often contains a different number of chains than does the crystallographic asymmetric unit. Examples are given in the article on biological units.
ReferencesReferences
- ↑ Hendrix RW, Johnson JE. Bacteriophage HK97 capsid assembly and maturation. Adv Exp Med Biol. 2012;726:351-63. doi: 10.1007/978-1-4614-0980-9_15. PMID:22297521 doi:10.1007/978-1-4614-0980-9_15
- ↑ Gilakjan ZA, Kropinski AM. Cloning and analysis of the capsid morphogenesis genes of Pseudomonas aeruginosa bacteriophage D3: another example of protein chain mail? J Bacteriol. 1999 Dec;181(23):7221-7. PMID:10572124