Title : The four terminal components of the complement system are C-mannosylated on multiple
tryptophan residues
Abstract :
- 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
Output (sent_index, trigger,
protein,
sugar,
site):
- 10. Trp, , -, all modified Trp residues, Trp residues
- 10. present, , proteins, the thrombospondin type 1 repeats, -
- 2. C-mannosylated, , -, -, Trp
- 5. C-mannosylated, , proteins, -, -
- 7. C-mannosylated, , -, -, Trp residues
Output(Part-Of) (sent_index,
protein,
site):
*Output_Site_Fusion* (sent_index,
protein,
sugar,
site):