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PubMed1995

Signal transfer through three compartments: transcription initiation of the Escherichia coli ferric citrate transport system from the cell surface.

Transport of ferric citrate into cells of Escherichia coli K-12 involves two energy-coupled transport systems, one across the outer membrane and one across the cytoplasmic membrane. Previously, we have shown that ferric citrate does not have to enter the cytoplasm of E. coli K-12 to induce transcription of the fec ferric citrate transport genes. Here we demonstrate that ferric citrate uptake into the periplasmic space between the outer and the cytoplasmic membranes is not required for fec gene induction. Rather, FecA and the TonB, ExbB and ExbD proteins are involved in induction of the fec transport genes independent of their role in ferric citrate transport across the outer membrane. The uptake of ferric citrate into the periplasmic space of fecA and tonB mutants via diffusion through the porin channels did not induce transcription of fec transport genes. Point mutants in FecA displayed the constitutive expression of fec transport genes in the absence of ferric citrate but still required TonB, with the exception of one FecA mutant which showed a TonB-independent induction. The phenotype of the FecA mutants suggests a signal transduction mechanism across three compartments: the outer membrane, the periplasmic space and the cytoplasmic membrane. The signal is triggered upon the interaction of ferric citrate with FecA protein. It is postulated that FecA, TonB, ExbB and ExbD transfer the signal across the outer membrane, while the regulatory protein FecR transmits the signal across the cytoplasmic membrane to FecI in the cytoplasm. FecI serves as a sigma factor which facilitates binding of the RNA polymerase to the fec transport gene promoter upstream of fecA.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗

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[DocuMed--a personal computer program system for basic documentation and ICD statistics based on SNOMED].

Of the different medical classification systems ICD only has endured on the long time, and through the german government regulations from 1985 (Bundespflegesatzordnung) ICD has become a must to all hospital departments for administration purposes. As a clinical and scientific system for encoding of diagnosis and treatment procedures ICD has been proved to be of minor suitability. SNOMED, a medical classification system derived from a pathological description of diseases seemed first to fulfill all the wishes clinicians have; but the very little use over the 12 years since its publication demonstrates its poor acceptance. This might be due to the time consuming and lavish procedure of documentation in SNOMED, as entries have to be made in 7 categories. DocuMed, which is a microcomputer program and database on the one hand and a medical classification system on the other, seems to provide interesting features. For minimal documentation it only needs entries in the category of diagnosis, a term not present in SNOMED; for more detailed documentation requirements DocuMed provides similar categories as SNOMED with references to the latter and to ICD.

Bone Diseases↗