A New 4-Nitrotoluene Degradation Pathway in aMycobacterium Strain

ABSTRACT Mycobacterium sp. strain HL 4-NT-1, isolated from a mixed soil sample from the Stuttgart area, utilized 4-nitrotoluene as the sole source of nitrogen, carbon, and energy. Under aerobic conditions, resting cells of the Mycobacterium strain metabolized 4-nitrotoluene with concomitant release of small amounts of ammonia; under anaerobic conditions, 4-nitrotoluene was completely converted to 6-amino-m-cresol. 4-Hydroxylaminotoluene was converted to 6-amino-m-cresol by cell extracts and thus could be confirmed as the initial metabolite in the degradative pathway. This enzymatic equivalent to the acid-catalyzed Bamberger rearrangement requires neither cofactors nor oxygen. In the same crucial enzymatic step, the homologous substrate hydroxylaminobenzene was rearranged to 2-aminophenol. Abiotic oxidative dimerization of 6-amino-m-cresol, observed during growth of theMycobacterium strain, yielded a yellow dihydrophenoxazinone. Another yellow metabolite (λmax, 385 nm) was tentatively identified as 2-amino-5-methylmuconic semialdehyde, formed from 6-amino-m-cresol bymeta ring cleavage.

High Frequency cDNA Recombination of the Saccharomyces Retrotransposon Ty5: The LTR Mediates Formation of Tandem Elements

Retroelement cDNA can integrate into the genome using the element-encoded integrase, or it can recombine with preexisting elements using the recombination system of the host. Recombination is a particularly important pathway for the yeast retrotransposon Ty5 and accounts for ∼30% of the putative transposition events when a homologous substrate is carried on a plasmid and ∼7% when the substrate is located at the chromosomal URA3 locus. Characterization of recombinants revealed that they are either simple replacements of the marker gene or tandem elements. Using an assay system in which the donor element and recombination substrates are separated, we found that the long terminal repeats (LTRs) are critical for tandem element formation. LTR-containing substrates generate tandem elements at frequencies more than 10-fold higher than similarly sized internal Ty5 sequences. Internal sequences, however, facilitate tandem element formation when associated with an LTR, and there is a linear relationship between frequencies of tandem element formation and the length of LTR-containing substrates. We propose that recombination is initiated between the LTRs of the cDNA and substrate and that internal sequences promote tandem element formation by facilitating sequence alignment. Because of its location in subtelomeric regions, recombinational amplification of Ty5 may contribute to the organization of chromosome ends.

Prorenin is present in human red blood cells

We looked for the presence of prorenin in erythrocytes from normal subjects (n = 8), hypertensive patients (n = 8), and pregnant women (n = 8). Angiotensin I generation was measured at 37 °C, pH 5.7, in the presence of homologous substrate (1400 ng/mL) before and after trypsin activation (100 μg/mL) in (A) haemolyzed erythrocytes, (B) supernatants of haemolyzed erythrocytes, and (C) in the sixth washing of erythrocytes diluted 1:1 with a 0.1 M Tris buffer containing 0.5% bovine serum albumin and protease inhibitors. Haemolyzed erythrocytes generated angiotensin I only after trypsin treatment, and the rate of generation was the same (A) before and (B) after centrifugation at 20000g, indicating the absence of prorenin bound to the cell membranes. When aliquots of the last washing of erythrocytes (C) were tested for angiotensin I generation before and after trypsin, they did not generate angiotensin I, indicating that residual prorenin from the plasma was no longer present in our preparation. Angiotensin I generation by trypsin-treated A and B was completely abolished by preincubation with anti-renin serum. The level of prorenin was not significantly different in the erythrocytes from normal, hypertensive, and pregnant subjects (68 ± 10, 58 ± 7 and 107 ± 17 pg angiotensin I∙mL−1∙h−1, ns) in spite of their very different plasma levels (21 ± 2.5, 17 ± 2.4 and 110 ± 12 ng angiotensin I∙mL−1∙h−1, p < 0.01 for pregnant women compared with both normal and hypertensive subjects). Our data show that prorenin is present in human erythrocytes in fairly constant and clearly detectable amounts, thus suggesting a possible intracellular role for it.Key words: inactive renin, intracellular prorenin, erythrocytes, prorenin.

A method for determination of renin activity in dog's plasma and renal tissue

A procedure based on that of Boucher et al. (Can. J. Physiol. Pharmacol. 45, 881 (1967)) for the microdetermination of plasma renin activity in the rat is described for the measurement of the same parameter in 1 ml of dog plasma. This procedure permits serial determinations and uses homologous substrate with incubation with Dowex 50W-X2 (NH4+) at pH 5.5 for 12 h. The results are expressed as nanograms of angiotensin formed per milliliter of plasma after 12 h of incubation. The mean plasma renin activity in healthy dogs was 1.04 ng/ml per h, ± 1.03 S.D., with a range of 0–3.3 ng. This procedure was applied to the measurement of renin activity in renal tissue.