C6 EPITOPE EXPRESSION BY AN UNRELATED ANTISENSE CDNA CLONE - AN INADVERTENT SURFACE-SIMULATION MIMOTOPE

A cDNA clone which directs the expression of a fusion protein reacting with anti-C6 antibodies has been isolated and sequenced. A synthetic peptide corresponding to the 14 C-terminal residues of the expressed p rotein elicited the production of antibodies which are specific for na tive C6, confirming the presence of a C6 epitope on the expressed prot ein. However, analysis of the intron-exon boundaries of a correspondin g genomic clone revealed that the expression clone is in antisense ori entation, and is therefore not C6 cDNA. Comparison of the sequences of the expression clone and expressed protein with those for C6 have not demonstrated any significant sequence homology. It is therefore appar ent that what has been cloned is a mimotope for C6 which includes in i ts continuous sequence an epitope that is conformational in C6 and not represented as a continuous sequence in the C6 molecule. Although thi s was not the purpose of the investigation, these results confirm that screening random expression libraries with antibodies may be an alter native to the synthetic peptide approach to obtain mimotopes reacting with particular antibodies.