Primary structure of three distinct isoabrins determined by cDNA sequencing. Conservation and significance.
A family of toxic proteins, the isoabrins, which possess N-glycosylase activity toward eukaryotic 28 S r-RNA, may have potential use in cancer chemotherapy. By polymerase chain reaction techniques, cDNA clones of three isoabrins, carrying A and B-chain sequences, were isolated and their nucleotide sequences were determined. The isoabrins consist of an A-chain comprised of 250 of 251 amino acids, followed by a 10 amino acid linker and a B-chain of 267 amino acids. There is substantial conservation in the B-chain of the three isoabrins, with less than six amino acid substitutions, whereas as many as 46 amino acid substitutions occur in the A-chains. Based on the relationships between the biological activities and the putative amino acid sequences of the isoabrins, three isoabrins, abrin-a, -b and -d, could be identified and the potential epitope of immunological response of these isoabrins could be assigned.
Hung
C H
CH
Institute of Biochemistry, College of Medicine, National Taiwan University, Taipei, R.O.C.
Lee
M C
MC
Lee
T C
TC
Lin
J Y
JY
D000036:Abrin / Q000737:chemistry* / Q000235:genetics / Q000276:immunology; D000595:Amino Acid Sequence; D001483:Base Sequence; D003429:Cross Reactions; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid
D000036:Abrin