The sucrase-isomaltase complex: primary structure, membrane-orientation, and evolution of a stalked, intrinsic brush border protein

Cell. 1986 Jul 18;46(2):227-34. doi: 10.1016/0092-8674(86)90739-7.


The complete primary structure (1827 amino acids) of rabbit intestinal pro-sucrase-isomaltase (pro-SI) was deduced from the sequence of a nearly full-length cDNA. Pro-SI is anchored in the membrane by a single 20 amino acid segment spanning the bilayer only once. The amino-terminal, cytoplasmic domain consists of 12 amino acids and is not preceded by a cleaved leader sequence. This suggests a dual role for the membrane-spanning segment as an uncleaved signal for membrane insertion. This is followed by a 22 residue serine/threonine-rich, probably glycosylated, stretch, presumably forming the stalk on which the globular, catalytic domains are directed into the intestinal lumen. Following this is a high degree of homology between the isomaltase and sucrase portions (41% amino acid identity), indicating that pro-SI evolved by partial gene duplication.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Biological Evolution
  • Cell Membrane / analysis
  • Cell Membrane / metabolism
  • DNA / isolation & purification
  • Genes
  • Intestinal Mucosa / metabolism
  • Membrane Proteins / isolation & purification*
  • Microvilli / analysis
  • Microvilli / metabolism*
  • Multienzyme Complexes / isolation & purification*
  • Protein Processing, Post-Translational
  • Rabbits
  • Sucrase-Isomaltase Complex / genetics
  • Sucrase-Isomaltase Complex / isolation & purification*


  • Membrane Proteins
  • Multienzyme Complexes
  • DNA
  • Sucrase-Isomaltase Complex

Associated data

  • GENBANK/M14046