We have determined and analyzed the nucleic acid sequence of a 14,855-bp region that contains the complete gene cluster encoding the 4-hydroxyphenylacetic acid (4-HPA) degradative pathway of Escherichia coli W (ATCC 11105). This catabolic pathway is composed by 11 genes, i.e., 8 enzyme-encoding genes distributed in two putative operons, hpaBC (4-HPA hydroxylase operon) and hpaGEDFHI (meta-cleavage operon); 2 regulatory genes, hpaR and hpaA; and the gene, hpaX, that encodes a protein related to the superfamily of transmembrane facilitators and appears to be cotranscribed with hpaA. Although comparisons with other aromatic catabolic pathways revealed interesting similarities, some of the genes did not present any similarity to their corresponding counterparts in other pathways, suggesting different evolutionary origins. The cluster is flanked by two genes homologous to the cstA (carbon starvation protein) and tsr (serine chemoreceptor) genes of E. coli K-12. A detailed genetic analysis of this region has provided a singular example of how E. coli becomes adapted to novel nutritional sources by the recruitment of a catabolic cassette. Furthermore, the presence of the pac gene in the proximity of the 4-HPA cluster suggests that the penicillin G acylase was a recent acquisition to improve the ability of E. coli W to metabolize a wider range of substrates, enhancing its catabolic versatility. Five repetitive extragenic palindromic sequences that might be involved in transcriptional regulation were found within the cluster. The complete 4-HPA cluster was cloned in plasmid and transposon cloning vectors that were used to engineer E. coli K-12 strains able to grow on 4-HPA. We report here also the in vitro design of new biodegradative capabilities through the construction of a transposable cassette containing the wide substrate range 4-HPA hydroxylase, in order to expand the ortho-cleavage pathway of Pseudomonas putida KT2442 and allow the new recombinant strain to use phenol as the only carbon source.Although most of our current knowledge about the general bacterial metabolic pathways has been derived from the analysis of Escherichia coli, very few data are available about the ability of this microorganism to grow on aromatic compounds other than amino acids. It has been shown that E. coli B, C, and W, but not K-12 strains, are able to degrade 4-hydroxyphenylacetic acid (4-HPA) and homoprotocatechuate (3,4-hydroxyphenylacetate) (HPC) via an inducible, chromosomally encoded meta-cleavage pathway (8, 10).The HPC degradative operon of E. coli C has been partially cloned (25,43), and some of its products have been characterized (16-18, 40-42, 44, 48). In addition, we have previously demonstrated that the first step in the 4-HPA degradation in E. coli W, i.e., the formation of HPC, is catalyzed by a twocomponent aromatic hydroxylase (38,39). This enzyme is encoded by two genes which appear to be part of the same operon (38). The homologous 4-HPA hydroxylase operon of E. coli C has been also cloned and partially sequenced (38...

SummaryThe PhaF is a nucleoid-associated like protein of Pseudomonas putida KT2442 involved in the polyhydroxyalkanoate (

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We report the complete nucleotide sequence of the gene cluster encoding the 3-(3-hydroxyphenyl)propionate (3-HPP) catabolic pathway of Escherichia coli K-12. Sequence analysis revealed the existence of eight genes that map at min 8 of the chromosome, between the lac and hemB regions. Six enzyme-encoding genes account for a flavin-type monooxygenase (mhpA), the extradiol dioxygenase (mhpB), and the meta-cleavage pathway (mhpCDFE). The order of these catabolic genes, with the sole exception of mhpF, parallels that of the enzymatic steps of the pathway. The mhpF gene may encode the terminal acetaldehyde dehydrogenase (acylating) not reported previously in the proposed pathway. Enzymes that catalyze the early reactions of the pathway, MhpA and MhpB, showed the lowest level of sequence similarity to analogous enzymes of other aromatic catabolic pathways. However, the genes mhpCDFE present the same organization and appear to be homologous to the Pseudomonas xyl, dmp, and nah meta-pathway genes, supporting the hypothesis of the modular evolution of catabolic pathways and becoming the first example of this type of catabolic module outside the genus Pseudomonas. Two bacterial interspersed mosaic elements were found downstream of the mhpABCDFE locus and flank a gene, orfT, which encodes a protein related to the superfamily of transmembrane facilitators that might be associated with transport. All of the genes of the 3-HPP cluster are transcribed in the same direction, with the sole exception of mhpR. Inducible expression of the mhp catabolic genes depends upon the presence, in the cis or trans position, of a functional mhpR gene, which suggests that the mhpR gene product is the activator of the 3-HPP biodegradative pathway. The primary structure of MhpR revealed significant similarities to that of members of the IclR subfamily of transcriptional regulators. A 3-HPP catabolic DNA cassette was engineered and shown to be functional not only in enteric bacteria (E. coli and Salmonella typhimurium) but also in Pseudomonas putida and Rhizobium meliloti, thus facilitating its potential application to improve the catabolic abilities of bacterial strains for degradation of aromatic compounds.

The hpaB gene encoding an aromatic hydroxylase of Escherichia coli ATCC 11105, a penicillin G acylase-producing strain, has been cloned and expressed in E. coli K-12

No clear genotype-phenotype correlation was found. Patients' biochemical profiles did not reveal a relationship between sterol profiles and severity of disease. A skewed X-chromosome inactivation may explain the clinical phenotype in CDPX2 in some familial cases.

1 The isometric response to arginine-vasopressin (10-1o 10-7 M) was studied in 2 mm long rabbit arterial segments isolated from several vascular beds (cutaneous, pial, renal, coronary, muscular, mesenteric and pulmonary). 2 Vasopressin induced contraction in central ear (cutaneous), basilar (pial), renal, coronary and saphenous (muscular) arteries, but had no effect in mesenteric and pulmonary arteries; the order of potency for the contraction was: ear > basilar > renal > coronary > saphenous arteries. 3 Treatment with the blocker of nitric oxide synthesis NG-nitro-L-arginine methyl ester (L-NAME; 106-I0-M) increased significantly (P< 0.05) the contraction to vasopressin in ear (148% of control), basilar (150% of control), renal (304% of control), coronary (437% of control) and saphenous (235% of control) arteries. Removal of the endothelium increased significantly (P<0.05) the contraction to vasopressin in basilar (138% of control), renal (253% of control), coronary (637% of control) and saphenous (662% of control) arteries, but not in ear artery. Mesenteric and pulmonary arteries in the presence of L-NAME or after endothelium removal did not respond to vasopressin, as occurred in control conditions. 4 The specific antagonist for V1 vasopressin receptors d(CH2)5Tyr(Me)AVP (3 x 10-9-10-7 M) was more potent (pA2=9.3-10.1) than the antagonist for both VI and V2 vasopressin receptors desGly-d(CH2)5-D-Tyr(Et)ValAVP (10-7-10-6 M) (pA2 =7.4-8.4) to block the contraction to vasopressin of ear, basilar, renal and coronary arteries. 5 The specific V2 vasopressin agonist [deamino-Cys1, D-Arg8]-vasopressin (desmopressin) (10-1o-10-7 M) did not produce any effect in any of the arteries studied, with or without endothelium. 6 In arteries precontracted with endothelin-1, vasopressin or desmopressin did not produce relaxation. 7 These results suggest: (a) most arterial beds studied (5 of 7) exhibit contraction to vasopressin with different intensity; (b) the vasoconstriction to this peptide is mediated mainly by stimulation of V1 vasopressin receptors, and (c) endothelial nitric oxide may inhibit the vasoconstriction to this peptide, especially in coronary and renal vasculatures.