The amino acid sequence of the egg yolk storage protein phosvitin has been deduced from the nucleotide sequence of part of the chicken vitellogenin gene. Of the phosvitin sequence, 210 amino acids including the N-terminal residue are contained on one large exon, whereas the remaining six amino acids are encoded on the next exon. Phosvitin contains a core region of 99 amino acids, consisting of 80 serines, grouped in runs of maximally 14 residues interspersed by arginines, lysines, and asparagines. The serines of the core region are encoded by AGC and AGT codons exclusively and the arginines by AGA and AGG, which results in a continuous stretch of 99 codons with adenine in the first position. The N-terminal quarter of the phosvitin sequence contains 16 serines grouped in a cluster with alanines and threonines and coded mainly by TCX triplets. The C-terminal part includes 27 serines, preferentially coded by AGC and AGT, 13 histidine residues, and the sequence ...Asn-Gly-Ser... at which the carbohydrate moiety of phosvitin is attached. Heteroduplex formation between cloned DNAs from chicken and Xenopus vitellogenin genes shows that the phosvitin sequence contains a stretch of highly conserved sequence.

A chromosomal gene of Enterobacter cloacae encoding an outer membrane protein (OmpX) has been cloned. Overproduction of the OmpX protein decreased the quantity of porins in the outer membrane of the parental strain and of Escherichia coli HB101. The The outer membranes of gram-negative bacteria obtain their nonspecific permeability for hydrophilic solutes from the presence of porins, a class of proteins that form waterfilled diffusion channels (22). Lack of these proteins leads to resistance to most beta-lactam antibiotics and quinolones (1, 21). In a previous report (28), we described the cloning of a restriction fragment of Enterobacter cloacae chromosomal DNA that was associated with resistance to beta-lactam antibiotics in transformants both of Escherichia coli and of the parental E. cloacae strain. In these transformants, the amount of the porin proteins OmpF and OmpC present decreased, and an outer membrane protein of approximately 18 kDa was overproduced. In vitro transcription and translation of the recombinant plasmid showed that this protein was encoded by a gene on the cloned fragment. The function of the protein is still unknown, but its overproduction clearly interferes with the presence of OmpF and OmpC in the outer membrane. We propose the name OmpX for this protein, as long as its proper function is obscure. In the accompanying paper (29), the biological characterization of OmpX is presented. In this report, we present the nucleotide sequence of the ompX gene and the deduced amino acid sequence. From these data, some physical properties of OmpX are derived. MATERIALS AND METHODSBacterial strains and plasmids. The bacterial strains, plasmids, and bacteriophages used are listed in Table 1.Growth conditions. Bacteria were grown at 37°C in brain heart infusion broth (Oxoid Ltd.) supplemented when required with chloramphenicol (34 jig/ml Insertions of the transposable element -yb (11) in plasmid pJS04 were obtained as follows. DNA of plasmid pJS04 was introduced into the F' lac+-containing E. coli CE1304 by transformation. Transformants were selected on Iso-Sensitest agar (Oxoid CM471) containing chloramphenicol (34 ,ug/ml). Several transformants were subsequently mated with E. coli W3110 by filter mating on agar plates for 18 h at 37°C. Cells were collected from the filter, and the mixture was plated on Iso-Sensitest agar plates containing chloramphenicol and nalidixic acid (80 ,ug/ml). Transconjugants were screened subsequently for growth on Iso-Sensitest agar plates containing cephalothin (10 ,g/ml). The positions of the -yb sequence insertions were localized by restriction enzyme digestions.Analysis of plasmid-encoded proteins. Plasmid-encoded proteins were synthesized in vitro in a procaryotic DNAdirected transcription-translation system (Amersham, U.K.

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The outer membrane protein OmpX of Enterobacter cloacae shows high amino acid homology with virulence proteins PagC and Rck from Salmonella typhimurium and with Ail from Yersinia enterocolitica. Here we demonstrate a role for OmpX in the invasion of rabbit ileal tissue by E. cloacae. An organ culture system was used for maintenance of rabbit gut tissue during the experiments. The invasivenesses of three E. cloacae strains, which differed in OmpX content, were compared with each other and with that of Salmonella typhimurium TML (a highly invasive strain) and S. typhimurium LT7 (a noninvasive strain). There was no significant difference between the invasiveness of the wild type and that of an ompX deletion mutant strain of E. cloacae; they were equally as invasive or less invasive than S. typhimurium LT7. The invasiveness of an OmpX overproducer strain of E. cloacae was 10-fold higher than that of its immediate parent carrying only the multicopy plasmid, higher than that of S. typhimurium LT7, but lower than that of S. typhimurium TML. The invasiveness of E. cloacae thus varied directly with the level of OmpX in the outer membrane in rabbit ileal

A chromosomal gentamicin resistance determinant from Pseudomonas aeruginosa was cloned on a 2.4-kb fragment in the broad-host-range vector pLAFR3. Substrate profiles for eight aminoglycosides at three concentrations showed that resistance was due to aminoglycoside- (3)