Nucleotide sequence of cloned cDNA coding for preproricin

Eur J Biochem. 1985 Apr 15;148(2):265-70. doi: 10.1111/j.1432-1033.1985.tb08834.x.


The primary structure of a precursor protein that contains the toxic (A) and galactose-binding (B) chains of the castor bean lectin, ricin, has been deduced from the nucleotide sequence of cloned DNA complementary to preproricin mRNA. A cDNA library was constructed using maturing castor bean endosperm poly(A)-rich RNA enriched for lectin precursor mRNA by size fractionation. Clones containing lectin mRNA sequences were isolated by hybridization using as a probe a mixture of synthetic oligonucleotides representing all possible sequences for a peptide of the ricin B chain. The entire coding sequence of preproricin was deduced from two overlapping cDNA clones having inserts of 1614 and 1049 base pairs. The coding region (1695 base pairs) consists of a 24-amino-acid N-terminal signal sequence (molecular mass 2836 Da) preceding the A chain 267 amino acids, molecular mass 29 399 Da), which is joined to the B chain (262 amino acids, molecular mass 28 517) by a 12-amino-acid linking region (molecular mass 1385 Da).

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acids / isolation & purification
  • Base Sequence
  • Chemical Phenomena
  • Chemistry
  • Cloning, Molecular
  • DNA / isolation & purification*
  • Genetic Code
  • Protein Precursors / genetics*
  • RNA, Messenger / isolation & purification
  • Ricin / genetics*


  • Amino Acids
  • Protein Precursors
  • RNA, Messenger
  • preproricin
  • DNA
  • Ricin

Associated data

  • GENBANK/X02388