Reference

Tyrosine and tyrosinate fluorescence of bovine testes calmodulin: calcium and pH dependence

Tyrosine and tyrosinate fluorescence of bovine testes calmodulin: calcium and pH dependence. Pundak, Shlomo; Roche, Rodney S. (Dep. Chem., Univ. Calgary, Calgary, AB T2N 1N4, Can.). Biochemistry, 23(7), 1549-55 (English) 1984. CODEN: BICHAW. ISSN: 0006-2960. DOCUMENT TYPE: Journal CA Section: 6 (General Biochemistry) At physiol. pH, bovine testes calmodulin (t-CaM) upon excitation at 278 nm shows typical tyrosine fluorescence at 305 nm and a spectral band characteristic of emission from tyrosinate, at 330-350 nm. In addn., a new band at 312-320 nm appears upon excitation at 288 nm. The pH dependence of the excitation spectra demonstrates that the intense tyrosinate emission at 330-355 nm originates from direct excitation of ground-state tyrosinate. The tyrosinate emission shows complex pH dependence and reaches its highest intensities at pH 7.0 and 8.5, in both apo (Ca2+-free) and holo (Ca2+-satd.) t-CaM. 60-18-4 and 7440-70-2 which are cas registry numbers are also used here. The major contribution to the tyrosinate emission at 330-350 nm appears to originate from tyrosine-99. In holo CaM, the tyrosine emission at 305 nm is quenched at basic pH values and exhibits a sigmoidal pH titrn. curve with pK (apparent) 7.0. The tyrosine emission in apo t-CaM is weaker and is almost insensitive to changes in pH. The pH dependence of the emission at 316 nm is the same as the pH dependence of the tyrosine emission in both apo and holo t-CaM. The differences between the fluorescence of apo and holo CaM are attributed to a Ca2+-induced shift in the pKa of carboxylic side chains located in the immediate vicinity of the tyrosine residues. The enhancement of the fluorescence by Ca2+ is pH dependent and is maximal at pH 6.5. Above pH 8.0, there is almost no Ca2+ effect on the fluorescence. Conformational changes induced by variations in pH in the physiol. range, pH 6.0-8.0, as detected by the fluorescence measurements, suggests that changes in the levels of both Ca2+ and the proton regulate the conformation and also the biol. function of calmodulin. .

Hormonal regulation of sympathetic neuron development

Hormonal regulation of sympathetic neuron development. The effects of neonatal castration. Hamill, R. W.; Guernsey, L. A. (Neurol. Res. Lab., Monroe Community Hosp., Rochester, NY 14603, USA). Dev. Brain Res., 11(2), 303-7 (English) 1983.In this article, certain chemicals are used. Some of their cas registry numbers are 58-22-0 and 9036-22-0 CODEN: DBRRDB. ISSN: 0165-3806. DOCUMENT TYPE: Journal CA Section: 2 (Mammalian Hormones) The effects of neonatal castration on neuronal ontogeny were examd. in peripheral sympathetic ganglia in male Sprague-Dawley rats. Tyrosine hydroxylase (T-OH) [9036-22-0] activity, the rate-limiting enzyme in catecholamine biosynthesis and a marker of noradrenergic maturation, was examd. in the hypogastric and superior cervical ganglia (HG and SCG, resp.). Initial studies characterized the normal development of T-OH activity in HG. Neonatal castration at 10-11 days of age prevented the normal ontogeny of HG T-OH activity: T-OH activity failed to develop normally and was 17% of sham-operated littermate controls when examd. at 8 wk of age, and <5% when studied 10 wk after surgery. In contrast to the effects in HG, there was no change in enzyme activity in the SCG. Replacement therapy with testosterone [58-22-0] completely reversed the developmental alteration in enzyme activity. Evidently, hormonal factors modulate noradrenergic ontogeny in peripheral sympathetic ganglia, but these effects appear restricted to ganglia whose targets include hormonally dependent sex organs. .