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Properdin, the positive regulator of complement, is highly C-mannosylated
1Friedrich-Miescher Institut, CH-4058 Basel, Switzerland.
The Journal of Biological Chemistry
|July 6, 2000
Summary
Properdin, a key complement regulator, is heavily C-mannosylated at most of its tryptophan residues. This finding reveals widespread C-mannosylation in complement activation, offering a system to study this modification.
Area of Science:
- Biochemistry
- Immunology
- Proteomics
Background:
- Properdin regulates the alternative pathway of complement activation.
- Properdin contains thrombospondin type 1 repeats with WXXW motifs, sites for C-mannosylation.
- C-mannosylation is a post-translational modification involving a C-C bond to tryptophan.
Purpose of the Study:
- To investigate the C-mannosylation pattern of human properdin.
- To determine the extent and location of C-mannosylation in properdin.
- To explore the significance of C-mannosylation in complement proteins.
Main Methods:
- Mass spectrometry analysis of properdin.
- Edman degradation for protein sequencing.
- Identification of modified tryptophan residues.
Main Results:
- Human properdin contains 20 tryptophan residues, 17 within WXXW motifs.
- Fourteen tryptophan residues in properdin were found to be 100% C-mannosylated.
- This is the first reported protein with a majority of tryptophan residues C-mannosylated.
Conclusions:
- Properdin exhibits extensive C-mannosylation, particularly at WXXW motifs.
- C-mannosylated proteins are present at multiple stages of complement activation.
- The complement system provides an ideal platform for studying the function of C-mannosylation.