Protein C-mannosylation: facts and questions.

Among the posttranslational modifications of proteins, glycosylation is probably the most abundant one. Two main types of protein glycosylation have been known for several years, namely N-glycosylation and O-glycosylation. Their biochemical properties, structure and biosynthesis, have been described extensively. Their biological functions are also known for a number of proteins, although in many cases the function remains speculative despite continuous efforts. A few years ago, a new type of protein glycosylation was found, which is different from the above-mentioned ones. It was called C-glycosylation, since the sugar is linked to the protein through a carbon-carbon bond. This article reviews the biochemistry of C-glycosylation, the biosynthetic pathway and structural requirements. Possible biological functions of this modification are also discussed.

The four terminal components of the complement system are C-mannosylated on multiple tryptophan residues.

C-Mannosylation is a unique form of protein glycosylation, involving the C-glycosidic attachment of a mannosyl residue to the indole moiety of Trp. In the two examples found so far, human RNase 2 and interleukin-12, only the first Trp in the recognition motif WXXW is specifically C-mannosylated. To establish the generality of protein C-mannosylation, and to learn more about its mechanism, the terminal components of the human complement system (C6, C7, C8,and C9), which contain multiple and complex recognition motifs, were examined. Together with C5b they form the cytolytic agent, the membrane attack complex. These are the first proteins that are C-mannosylated on more than one Trp residue as follows: six in C6, four in C7, C8alpha, and C8beta, and two in C9. Thus, from the 113 Trp residues in the complete membrane attack complex, 50 were found to undergo C-mannosylation. The other important finding is that in C6, C7, C8, and C9 Trp residues without a second Trp (or another aromatic residue) at the +3 position can be C-mannosylated. This shows that they must contain an additional C-mannosylation signal. Whether this is encoded in the primary or tertiary structure is presently unknown. Finally, all modified Trp residues are part of the highly conserved core of the thrombospondin type 1 repeats present in these proteins. Since this module has been found in a large number of other proteins, the results suggest further candidates for C-mannosylation.

[Results of examination of the reproductive organs of female workers in the textile industry]. / Wyniki badania narzadu rodnego kobiet zatrudnionych w przemysle dziewiarskim.

595 women, knitting-industry workers, were examined. This number constituted 47% of all employees of the knitting plant. 125 of those women were pregnant. Among non-pregnant women 35% exhibited reproductive organ pathologies. Of pregnant women 61% exhibited pregnancy complications. The prevalent pathologies of reproductive organs were uterine cervix erosion--37.8%, vaginitis--23.9%, and menstruation disturbances--12.8%. Of pregnancy complications anaemia--47.8%, early gestoses--27.8%, and vaginitis--6.6% prevailed. The working women indicated a statistically significant dependence between the posture at work and prevalence of gynecopathies. Most pathologies affected women walking at work, whereas, least pathologies were observed in those working at sitting posture.