PubMed · 746703
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P Schubert. 1978. [Transneural transport processes].. https://pubmed.ncbi.nlm.nih.gov/746703/
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Renin-angiotensin (RA) system plays an important role in cardiovascular homeostasis. Here, we have described the recent progress in our study of renin release as well as the cellular action of angiotensin II. (1) Microdissection of an isolated afferent artery with or without macula densa (MD) has revealed that renin release is regulated by NaCl exposure to MD. Furosemide, prostaglandins (PGE2 and PGI2) and adenosine modulate its function. (2) Angiotensin (ang) II increases cytosolic free calcium and induces the formation of inositolphosphates in vascular smooth muscle cells. Deduced protein structure of ang II receptor (AT1-R) cDNA has indicated the presumed link of AT1-R with phospholipase C. Through the cellular action, ang II has been reported to regulate gene expression.
We have studied the in vivo chemical accessibility of 16S rRNA residues A349-G1505 in the small subunit of the Escherichia coli ribosome. Exponentially growing E. coli cultures were reacted with dimethyl sulfate, and the reactive sites on the 16S ribosomal RNA were analyzed by reverse transcription, an assay which detects reactions at N1-A and N3-C. In agreement with previous in vitro results, three regions of 16S RNA appeared particularly reactive to dimethyl sulfate: hairpin 27 (residues A892-A915) of the central domain, and hairpin 33-33A (residues A994-C1037) and the tip of hairpin 41 (residues A1256-A1275), both from the 3' major domain. These three regions contained 52% of the reactive residues but only 8% of the residues scanned. In contrast to previous in vitro results, three small sections of 16S RNA appeared protected: the tip of hairpins 26 (residue A845) and 31 (residues A968-A969), and residues A1418, A1441, and A1483 of the middle body of hairpin 44. Four of the dimethyl sulfate reactive sites (A831, C948, A1019, and C1192) are located in positions usually assumed to be double-stranded (helices 26, 30, 33-33A, and 34), which suggests alternative structures for these helices at least during part of the translation process, as if the residues in question belonged to "conformational switches." The addition of chloramphenicol protected residues A831, A1035-A1036, and A1503, which suggests that they belong to the mobile regions of the elongating ribosome, and become exposed during some transition(s) from one ribosomal state to the other during the elongation cycle.
Two new nucleosides have been identified in unfractionated transfer RNA of two thermophilic bacteria, Thermodesulfobacterium commune, and Thermotoga maritima, six hyperthermophilic archaea, including Pyrobaculum islandicum, Pyrococcus furiosus and Thermococcus sp. and two mesophilic archaea, Methanococcus vannielii and Methanolobus tindarius. Structures were determined primarily by mass spectrometry, as 3-hydroxy-N-[[(9-beta-D-ribofuranosyl-9H-purin-6- yl)amino]carbonyl]norvaline, (hn6A), structure 1, and 3-hydroxy-N-[[(9-beta-D-ribofuranosyl-9H-2-methylthiopurin-6- yl)amino]carbonyl]norvaline (ms2hn6A), 2. The amino acid side chain was characterized as 3-hydroxynorvaline (3) by gas chromatography-mass spectrometry of the trimethylsilyl derivative after cleavage from 1 and 2 by alkaline hydrolysis. Evidence for the amino acid-purine carbamoyl linkage was obtained from the collision-induced dissociation mass spectrum of trimethylsilylated 1, and the total structure was confirmed by chemical synthesis of 1.