Capsule biosynthesis

The neuA (ORF 25) and neuB (ORF 24) gene products were functionally characterized by complementation of E. coli K1 mutants EV5 and EV24 that are defective in K1 polysialic acid capsule biosynthesis. The EV5 mutant was complemented to wild-type capsule production by introduction of neuA, and the EV24 mutation complemented by the neuB gene. 

Boulnois, G. J., Roberts, I. S., Hodge, R., Hardy, K. R., Jann, K. B., and Timmis, K. N., 1987, Analysis of the K1 capsule biosynthesis genes of Escherichia coli Definition of three functional regions for capsule production. Mol. Gen. Genet. 208 242-246. 

Further work on the biosynthesis of alkaloids by fractions of the latex of seed capsules of P. somniferum has been published.39... 

On-the-fly comparison of two gene clusters from Streptococcus pneumoniae for the biosynthesis of differing polysaccharide capsule structures. Sequences will be selected from the public databases for the generation of comparison files and subsequent visualization in ACT. 

The example describes the creation of a comparison between two entries uploaded into WebACT from the public DNA database. Each entry contains the DNA sequence and annotation for a gene cluster from S. pneumoniae encoding the biosynthesis of a particular polysaccharide capsule structure. Each strain of S. pneumoniae carries 1 version of the gene cluster out of a possible 90 (17). The different capsule types are conventionally determined by serotyping. The capsule forms the outer coating of these bacterial cells and differences in their structure affect interactions with the human host. 

An early key intermediate in benzylisoquinoline biosynthesis is (57), which by decarboxylation affords (59) this in turn leads to (61) and on to alkaloids (Scheme 2). Confirmation of this pathway has come from a study using cell-free preparations of P. somniferum stems and seed capsules. It was found that this preparation catalysed the formation of (57), (59), and (61) from dopamine (54) plus 3,4-dihydroxyphenylpyruvic acid (55) without the addition of 5-adenosyl-methionine, NADPH, and pyridoxal phosphate, the reaction stopped at (57). The formation of the alkaloids reticuline, thebaine, codeine, and morphine, produced by whole plants, could not be detected with this cell-free system. The results confirm not only the intermediacy of (57) and (59) in benzylisoquinoline biosynthesis, but also the involvement of (54) and (55). 

E.A. Troy, Chemistry and biosynthesis of the poly(-D-glutamyl) capsule in Bacillus licheniformis. I. Properties of the membrane-mediated biosynthetic reaction, J. Biol. Chem. 248 (1973) 305—315. 

---