This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Structure & Function of Protein, Subject name: Biochemistry
[{'content': 'Which of the following factors gives the elastin molecule the ability to stretch and recoil? \nSelect and explain. \nA. Hydroxylation of proline and lysine rich regions, B. Cross-links between lysine residues, C. Elastase activity, D. Triple helix formation', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. B. Cross-links between lysine residuesElastin is an elastic protein found in lungs, dermis, large arteries, ligaments, vocal cords and the ligamentum flavum. Its ability to stretch is conferred by interchain crosslinks between lysine residues.Similar to collagen, elastin is synthesized in several steps. It begins as a large precursor molecule, tropoelastin. Tropoelastin is secreted into the extracellular matrix, where it interacts with Fibrillin-containing microfibril scaffolds to form elastic fibers. The lysine residues on separate elastin molecules interact in a process called desmosine cross-chain linking, providing elastin with its stretch.', 'role': 'assistant'}]