Final answer:
Elastin polypeptides undergo cross-linking to form desmosine cross-links, providing elastin with its characteristic rubber-like elasticity.
Step-by-step explanation:
The cross-linking of elastin polypeptides forms a network structure known as desmosine cross-link. Elastin, which originates from the precursor tropoelastin, undergoes oxidative deamination of specific lysyl residues to form aldehydes known as allysine. In this process, three allysyl residues and one unaltered lysyl residue interact to create the desmosine cross-links, which are responsible for the unique rubber-like elasticity of elastin found in various connective tissues. These cross-links are significant for the functioning of several tissues where flexibility and resilience are essential, like the lungs, arteries, and elastic ligaments.