desmosine and lysinenorleucine

Elastin is an important extracellular matrix protein that contributes to the elasticity of cells, tissues, and organs. Although crosslinking amino acids such as desmosine and isodesmosine have been identified in elastin, details regarding the structure remain unclear. In this study, an elastin crosslinker, lysinonorleucine, was chemically synthesized and detected in hydrolyzed bovine ligament and eggshell membrane samples utilizing tandem mass spectrometry. Merodesmosine, another crosslinker of elastin, was also measured in the same samples using the same analytical method. The resulting data should aid in the elucidating the crosslinking structure of elastin and eggshell membranes.

Topics: Animals; Cattle; Desmosine; Egg Shell; Elastin; Ligaments

Elastin is an essential vertebrate protein responsible for the elasticity of force-bearing tissues such as those of the lungs, blood vessels, and skin. One of the key features required for the exceptional properties of this durable biopolymer is the extensive covalent cross-linking between domains of its monomer molecule tropoelastin. To date, elastin's exact molecular assembly and mechanical properties are poorly understood. Here, using bovine elastin, we investigated the different types of cross-links in mature elastin to gain insight into its structure. We purified and proteolytically cleaved elastin from a single tissue sample into soluble cross-linked and noncross-linked peptides that we studied by high-resolution MS. This analysis enabled the elucidation of cross-links and other elastin modifications. We found that the lysine residues within the tropoelastin sequence were simultaneously unmodified and involved in various types of cross-links with different other domains. The Lys-Pro domains were almost exclusively linked via lysinonorleucine, whereas Lys-Ala domains were found to be cross-linked via lysinonorleucine, allysine aldol, and desmosine. Unexpectedly, we identified a high number of intramolecular cross-links between lysine residues in close proximity. In summary, we show on the molecular level that elastin formation involves random cross-linking of tropoelastin monomers resulting in an unordered network, an unexpected finding compared with previous assumptions of an overall beaded structure.

Topics: 2-Aminoadipic Acid; Animals; Biopolymers; Cattle; Desmosine; Dipeptides; Elastin; Humans; Lysine; Protein Domains; Tropoelastin

Elastin from both elastofibroma and control skin samples was analyzed by means of pancreatic elastase digestion and subsequent biochemical studies, such as for elastin content and amino acid composition. Elastin of elastofibroma was more resistant to elastase digestion than that of controls. Elastin content was increased almost twice (wet weight) or three times (dry weight) in elastofibroma. The amino acid composition had the characteristics of elastin; however, the cross-linking amino acids such as desmosine, isodesmosine, and lysinonorleucine were increased in elastofibroma when compared with controls. An electron microscopic study showed that the interspersed cells had prominent intermediate filaments without any periodicity, pinocytotic vesicles, rough endoplasmic reticulum, and other organelles. These cells were considered to be fibroblasts not myofibroblasts. Therefore, it could be supposed that fibroblasts newly form an elastin that has a slightly different amino acid composition from that of controls.

Topics: Aged; Amino Acids; Desmosine; Dipeptides; Elastin; Female; Fibroma; Humans; Isodesmosine; Microscopy, Electron; Pancreas; Pancreatic Elastase; Shoulder; Skin Neoplasms