The phenol-phase soluble lipopolysaccharide isolated from Escherichia coli 0:157 by the hot phenol-water extraction procedure was shown by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, periodate oxidation, methylation, and 13C and 1H nuclear magnetic resonance studies to be an unbranched linear polysaccharide with a tetrasaccharide repeating unit having the structure: (formula; see text) The serological cross-reactivity of E. coli 0:157 with Brucella abortus, Yersinia enterocolitica (serotype 0:9), group N Salmonella, and some other E. coli species can be related immunochemically to the presence of 1,2-glycosylated N-acylated 4-amino-4, 6-dideoxy-alpha-D-mannopyranosyl residues in the O-chains of their respective lipopolysaccharides.

The autocatalytic processing of the streptococcal cysteine protease zymogen (proSCP) to active streptococcal cysteine protease (SCP) was investigated in vitro using purified protein from Streptococcus pyogenes strain B220. It was found that the autocatalytic maturation of the zymogen proceeds through the sequential appearance of at least six intermediates, five of which were characterized through a combination of N-terminal sequencing and MS. Intermediates were identified as resulting from cleavages after Lys26, Asn41, Lys101, Ala112, and Lys118. Time-course studies of the proSCP processing gave a sigmoidal activity profile and indicated that proSCP catalyses its own transformation, mainly via an intermolecular processing mechanism. A similar sequential appearance of intermediates was observed when inactive Cys192Ser proSCP was treated with native, enzymatically active SCP, thus demonstrating that the maturation can exclusively proceed by a bimolecular mechanism. It was shown that proSCP, but not mature SCP, immobilized on a Sepharose resin is capable of liberating itself from the column, indicating that the zymogen is also capable of intramolecular processing. In order to test whether the amino acid sequences at the processing sites could be used for developing new, specific substrates, 3-amino benzoic acid octapeptide derivatives based on all five characterized amino acid sequences from the autoprocessing cleavage sites were synthesized and tested for activity. The 3-amino benzoic acid derivatives have k cat /K M values ranging from 1200 to 7700´m 21´s21 , making them very good endopeptidase substrates for SCP.

No abstract

No abstract

Can. J. Chem. 71, 644 (1993). The complete structure of the complex cell-wall C-polysaccharide from Streptococcus ptzeumotziae R36A was elucidated using a combination of high-resolution NMR spectroscopy and theoretical calculations. The C-polysaccharide is Faisant appel i une combinaison de RMN i haute rksolution et de calculs thkoriques, on a rksolu la structure complkte du C-polysaccharide complexe de la cellule de la paroi du Streptococcus ptzeumotziae R36A. Le C-polysaccharide est composk de l'unitk rkpktitive suivante : P-D-Glcp ~-P +~-~-D -A A T~ 1+4-a-D-GalpNAc 1+3-P-D-GalpNAc l+ 1 -ribitol-5-phosphate dans laquelle ATT est le 2-acktamido-4-amino-2,4,6-tridksoxygalactopyranoside. Le C-polysaccharide porte deux substituants phosphorylcholines par unit6 rkpktitive et elles sont situkes sur le 0 -6 de chacun des deux rksidus 2-acktamido-2-dksoxygalactopyranose. Les unites rkpktitives sont likes par un ester diphosphate du ribitol au 0 -6 du rksidu P-D-glucopyranosyle.[Traduit par la rkdaction]