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The third component of Xenopus complement: cDNA cloning, structural and functional analysis, and evidence for an
J D Lambris1, J Pappas, M Mavroidis
1Department of Pathology, University of Pennsylvania, Philadelphia 19104-6079.
European Journal of Immunology
|February 1, 1995
Summary
Researchers characterized the Xenopus C3 complement component, revealing conserved cleavage sites and a novel truncated C3 transcript with potential inhibitory functions.
Area of Science:
- Immunology
- Molecular Biology
- Amphibian Research
Background:
- Limited information exists on amphibian complement component 3 (C3) primary structure.
- Previous studies purified C3 from Xenopus laevis and axolotl.
Purpose of the Study:
- To elucidate the primary structure of Xenopus C3.
- To analyze C3 convertase and Factor I cleavage sites in Xenopus C3.
- To investigate evidence for alternative C3 forms in Xenopus.
Main Methods:
- cDNA sequencing of Xenopus C3.
- Analysis of deduced amino acid sequences for cleavage sites.
- Protein sequencing of C3 fragments.
- Screening of liver cDNA library.
- Reverse transcription polymerase chain reaction (RT-PCR).
Main Results:
- 95% of Xenopus C3 cDNA sequence obtained, showing 57% nucleotide and 52% amino acid identity to human C3.
- Conserved C3 convertase and Factor I cleavage sites (Arg-Ser) identified and confirmed.
- An unusual C3 clone with a significant deletion identified, suggesting a novel C3 transcript.
- RT-PCR confirmed a transcript encoding a truncated C3 molecule (102 kDa).
Conclusions:
- Xenopus C3 shares structural and functional similarities with human C3, including conserved cleavage sites.
- A novel, truncated Xenopus C3 transcript exists, potentially analogous to human truncated C3 with inhibitory roles.