Studies on two constituents of elastic tissue : elastin and the microfibrillar component

Abstract

Section A; Insoluble elastin was isolated from bovine aorta and ligaraentum nuchae by the use of guanidine and dithiothreitol in conjunction with collagenase, purified by affinity chromatography. The preparations were free from carbohydrate and exhibited amino acid compositions similar to that of alkali-purified elastin, with the exception of the concentration of some polar amino acid residues. N-terminal analyses indicated a very low level of polypeptide chain damage in the preparations. Upon mild alkaline treatment glycine was selectively liberated as amino-end group. Elastin from ligamentum nuchae was examined by electron microscopy, X-ray diffraction, optical polarisation analysis and dynamometry. It is suggested that elastin fibrils consist of a lateral array of primary filaments. Section B: The microfibrillar component of adult bovine ligamentum nuchae was isolated by solubilisation in guanidine-dithiothreitol followed by S-carboxymethylation and treatment with collagenase. The amino acid composition of the material was at variance to those previously reported for similar preparations. N-terminal analysis revealed glycine as the only end-group, at a concentration of 65.9 moles/106g of protein. This value, corresponding to a molecular weight of about 15,000 daltons, was in good agreement with the results of sedimentation equilibrium analyses.