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J Tagg

Publications and source records attributed to J Tagg.

13 recordsLinked to original sources
PubMed1994

Elucidation of the structure of SA-FF22, a lanthionine-containing antibacterial peptide produced by Streptococcus pyogenes strain FF22.

The antibacterial peptide SA-FF22, produced by the pathogen Streptococcus pyogenes strain FF22 was purified and features of its primary and secondary structure were characterised. Mass spectrometry demonstrated the pure peptide had a mass of 2794Da while, amino acid analysis revealed the presence of the unusual, thioether amino acids lanthionine and 3-methyllanthionine; thus SA-FF22 is a member of the group of antibacterial polypeptides termed lantibiotics. Furthermore, amino acid sequencing showed a unique sequence which was blocked at position 23 by a residue of the unsaturated amino acid 2,3-didehydrobutyrine. Carboxypeptidase-Y digestion could be used to demonstrate that serine occupies the C-terminal position only after complete oxidation of the thioether amino acid bridges, suggesting that the three-dimensional structure of the native peptide may prevent access of the enzyme to the C-terminus. Fragmentation of the native peptide with a variety of proteolytic enzymes failed to yield a peptide containing less than all three of the cross-linked lanthionine and methyllanthionine residues and demonstrated that all three thioether bridges overlapped. Analysis of the circular dichroism of SA-FF22 in various concentrations of 2,2,2-trifluoroethanol in water, SDS micelles and in the presence of artificial phospholipid vesicles suggested that there is significant change in its secondary structure from aqueous to lipophilic environments.

Alanine↗
PubMed1994

The mode of action of SA-FF22, a lantibiotic isolated from Streptococcus pyogenes strain FF22.

SA-FF22 is a lanthionine-containing bacteriocidal peptide isolated from Streptococcus pyogenes strain FF22. The peptide interacts closely with non-energised artificial phospholipid vesicles, as evidenced by a 'blue shift' in the fluorescent emissions associated with a tryptophan residue within the peptide sequence. Furthermore, SA-FF22 induced efflux of radiolabelled amino acids from artificially energised cytoplasmic membrane vesicles and arrested uptake of amino acids by intact cells. By measuring the decrease in membrane potential of both starved and energised SA-FF22-treated cells, and through the use of artificial planar membranes, a potential of approximately 100 mV was deduced as the minimum required to induce pore formation by SA-FF22. This threshold potential is independent of the orientation of the applied voltage (i.e. trans or cis orientations are equally effective). Single channel conductance measurements suggested that the pores formed by SA-FF22 are relatively unstable, short-lived and approximately 0.5-0.6 nm in diameter. This is somewhat smaller than those of the previously described, pore-forming lantibiotics and should not allow significant efflux of large molecules such as ATP. Thus, death of affected cells seems to result from membrane-potential disruption and subsequent exhaustion of the cells.

Alanine↗
PubMed1990

Applications of bacteriocin-like inhibitory substance (BLIS) typing in a longitudinal study of the oral carriage of beta-haemolytic streptococci by a group of Dunedin schoolchildren.

A longitudinal study of the distribution of oral beta-haemolytic streptococci in 103 children (ages 5-6 y) attending three Dunedin schools was initiated in February 1987. A total of 858 paired pharyngeal and saliva specimens were obtained in nine principal sampling sessions, the last being in May 1989. The detection rate of Lancefield group A streptococci in directly plated pharyngeal cultures (19.8%) was considerably higher than in the corresponding saliva cultures (5.1%). By contrast, Lancefield group F and serologically non-groupable beta-haemolytic Streptococcus anginosus tended to be more prevalent in saliva (10.9% positive) than in pharyngeal specimens (7.1%). Group A streptococci were recovered at least once from 59 (57.3%) of the subjects. Representative beta-haemolytic streptococcus isolates were typed according to their production of bacteriocin-like inhibitory substances (BLIS) and by traditional serological techniques. The epidemiological value of BLIS typing was particularly evident in that both BLIS-positive and BLIS-negative strains could be differentiated within serotypes M1, M12 and M22 and also the serologically not typable group A streptococcus isolates. Ten children consistently had small numbers of group A streptococci present in their pharyngeal cultures, for periods of at least 12 months. In six of these subjects the carried strain was M-type 4/BLIS-type 655. This study has shown that in young schoolchildren long-term carriage of a variety of species of beta-haemolytic streptococci with little associated clinical evidence of infection may be common.

Bacterial Typing Techniques↗