PRIMARY STRUCTURE OF CYANELLE PEPTIDOGLYCAN OF CYANOPHORA-PARADOXA - A PROKARYOTIC CELL-WALL AS PART OF AN ORGANELLE ENVELOPE

The peptidoglycan layer surrounding the photosynthetic organelles (cya nelles) of the protist Cyanophora paradoxa is thought to be a relic of their cyanobacterial ancestors. The separation of muropeptides by gel filtration and reverse-phase high-performance liquid chromatography r evealed four different muropeptide monomers. A number of muropeptides were identical in retention behavior to muropeptides of Escherichia co li, while others had remarkably long retention times with respect to t heir sizes, as indicated by gel filtration, Molecular mass determinati on by plasma desorption and matrix-assisted laser desorption ionizatio n mass spectrometry showed that these unusual muropeptides had molecul ar masses greater by 112 Da or a multiple thereof than those of ones c ommon to both species, Fast atom bombardment-tandem mass spectrometry of these reduced muropeptide monomers allowed the localization of the modification to D-glutamic acid. High-resolution fast atom bombardment -mass spectrometry and amino acid analysis revealed N-acetylputrescine to be the substituent (E. Pittenauer, E. R. Schmid, G. Allmaier, B. P fanzagl, W. Loffelhardt, C. Quintela, M. A. de Pedro, and W. Stanek, B iol, Mass Spectrom, 22:524-536, 1993). In addition to the 4 monomers a lready known, 8 dimers, 11 trimers, and 6 tetramers were characterized , An average glycan chain length of 51 disaccharide units was determin ed by the transfer of [U-C-14]galactose to the terminal N-acetylglucos amine residues of cyanelle peptidoglycan. The muropeptide pattern is d iscussed with respect to peptidoglycan biosynthesis and processing.