Escherichia coli, sequence-structure-function

The bacterium Escherichia coli produces more than 3,000 different proteins a human produces 25,000 to 35,000. In both cases, each type of protein has a unique three-dimensional structure and this structure confers a unique function. Each type of protein also has a unique amino acid sequence. Intuition suggests that the amino acid sequence must play a fundamental role in determining the three-dimensional structure of the protein, and ultimately its function, but is this supposition cor-... 

In an Escherichia coli expression system for the aqualysin I precursor, the precursor is processed autoproteolytically into the mature 28-kDa enzyme by treatment at 65 ° C.23) In this case, the N-terminal pro-sequence is required for the production of active enzyme and functions to stabilize the precursor structure.283 The C-terminal pro-sequence is not essential for the production of active aqualysin 1,293 but seems to be involved in the translocation of the precursor across the cytoplasmic membrane.303 In a Thermus thermophilus expression system,313 the C-terminal pro-sequence is required for the production and extracellular secretion of active aqualysin I.323 In an E. coli expression system for the subtilisin E gene, the N-terminal pro-sequence is essential for the production of active enzyme,333 as in the case of aqualysin I. The requirement of the pro-sequence is also shown in vitro for the refolding of the inactive mature protein to an active enzyme.34 353 The functions of the N-terminal pro-sequences of aqualysin I and subtilisin E seem to be similar. 

Marolda, C.L., Valvano, M.A. Promoter region of the Escherichia coli 07-specific lipopolysaccharide gene cluster structural and functional characterization of an upstream untranslated mRNA sequence. J Bacteriol 180 (1998) 3070-3079. 

Archaea contain a stable 7S RNA species of unknown function, which is not associated with the ribosome. The 7S RNA gene from Halobacterium halobium NRC817 has been cloned and sequenced [120]. The sequence resembles the 7SL RNA of eucarya [85] and the 4.5S Escherichia coli) or sc Bacillus subtilis) RNAs of bacteria [121] in potential secondary structure. The 7SL RNA forms part of the signal-recognition particle, involved in protein translocation. The function of the 4.5S RNA is not known exactly, but it is known to be essential [122]. 

Fig. 39. (A) The ribbon diagram of subunit c and (B) peptide backbone model of a dodecameric ring of c-subunits of E. coli Fq viewd toward the membrane from the F, side. The C-terminal a-heiices are arranged in the inner ring and the N-terminal a-heiices in the peripheral ring. Residue Asp-61 located in the middle of the C-terminal sequence is indicated by a dot. Figure source (A) Fillingame, Girvin and Zhang (1995) Correlations of structure and function in subunit c of Escherichia coli FqF, ATP synthase. Biochem Soc Trans 23 763 (B) Groth and Walker (1997) Model of the c-subunit oligomer in the membrane domain ofF-A TPases. FEBS Lett 410 118.

J. S. Fetrow, A. Godzik, J. Skolnick. Functional Analysis of the Escherichia coli Genome Using the Sequence-to-Structure-... 

Fig. 5. Circular plot of features of the Escherichia coli K12 genome generated by Jena Prokaryotic Genome Viewer. The maxima and minima of the purine excess are located in the sequences ranges (maximum 1.548.120-1.550.620, minimum 3.929.072-3.931.572). The orbit descriptions are mostly self-explanatory. CDS [PDB] stands for genes for which three-dimensional protein structures are available in the Protein Data Bank. Note, that the origin of replication correlates with the purine excess minimum. In the original coloring scheme the CDS(+) and CDS(—) orbits are colored according to COG functional categories. All other orbits have a uniform color.

Galactose-l-P uridylyltransferase from Escherichia coli has been purified and its molecular properties characterized (29). It was found to have a M, of 80,(X)0 and to contain two subunits with a Mr of about 40,000. Active site studies showed the subunits to be functionally identical, so that it could be assumed that they are structurally identical (30). Nucleotide sequence analysis of the cloned gene gaU... 

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