PubMed · 13025475
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I BANGA, J BALO. 1953-01-03. Elastin and elastase.. https://doi.org/10.1038/171044a0
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Neutrophil proteinase 3 (Pr3) cleaves elastin and other matrix proteins, and is thought to cause lung tissue destruction in emphysema and cystic fibrosis. Its deleterious action is theoretically prevented by alpha1-antitrypsin, a serpin present in lung secretions. We have evaluated the anti-Pr3 activity of this inhibitor to decide whether it may play a physiologic proteolysis-preventing function in vivo. We show that (i). the oxidized inhibitor does not inhibit Pr3; (ii). the inhibitor competes favorably with elastin for the binding of Pr3, but is less efficient for inhibiting elastin-bound proteinase than for complexing free enzyme; and (iii). the inhibition takes place in at least two steps: the enzyme and the inhibitor first form a high-affinity reversible inhibitory complex EI* with an equilibrium dissociation constant K*i of 38 nM; EI* subsequently transforms into an irreversible complex EI with a first-order rate constant k2 of 0.04 s-1. Because the alpha1-antitrypsin concentration in the epithelial lining fluid is much higher than K*i, any Pr3 molecule released from neutrophils will be taken up as an EI* complex within much less than 1 s, indicating very efficient inhibition in vivo.
To investigate whether swapping native turns of a globular protein with an elastin-based turn sequence (VPGVG) can increase its thermostability, we have performed molecular dynamics simulations of wild-type chymotrypsin inhibitor 2 (CI2) and variants containing elastin-based turns at 10 degrees C and 40 degrees C. Wild-type CI2 is more stable at 10 degrees C, while both of the variant forms are more stable at 40 degrees C. Detailed analyses indicate that the elastin-based turns do indeed contribute to the inverse temperature behavior of the modified proteins. Therefore, swapping a wild-type turn sequence with an elastin-based turn provides a novel way to both improve stability of target proteins at body temperature and to possibly introduce a temperature-sensitive switch.
Magnetic resonance imaging and transvaginal ultrasonography in women of reproductive age suggest that the myometrium consists of inner and outer layers. It was hypothesized that these structural and functional differences in the myometrium might be associated with a variation in elastin distribution. Fifty-one hysterectomy specimens representing all phases of the normal menstrual cycle were studied by immunocytochemistry, orcein staining and image analysis. Elastin was present within the outer myometrial smooth muscle, but was less widely distributed in the inner smooth muscle. Immunoreactivity and staining were observed in the myometrial arteries and arterioles and within the basal portions of endometrial arterioles. Elastin was also present in perivascular tissue, particularly near the large vessels. More extravascular (i.e. perivascular and smooth muscle) elastin was present in the outer myometrium in all cases, although no distinct layering was observed. Semi-quantitative analysis of the elastin distribution in 11 full thickness specimens demonstrated a decreasing gradient from outer to inner myometrium rather than distinct layering. Contrary to previous reports, these data suggest that the external region of the myometrium is more elastic than the inner region and that elastin is found throughout the arteriolar tree of the human uterus.