Reticulocalbin, a novel endoplasmic reticulum resident Ca(2+)-binding protein with multiple EF-hand motifs and a carboxyl-terminal HDEL sequence

J Biol Chem. 1993 Jan 5;268(1):699-705.

Abstract

A novel Ca(2+)-binding protein, tentatively designated reticulocalbin, has been identified and characterized. Reticulocalbin is a luminal protein of the endoplasmic reticulum with an M(r) of 44,000 as revealed by biochemical analysis and immunofluorescence staining. The cDNA of reticulocalbin encodes a protein of 325 amino acids with an amino-terminal signal sequence of 20 amino acids. The protein has six repeats of a domain containing the high affinity Ca(2+)-binding motif, the EF-hand. Although oxygen-containing amino acids important for the positioning of Ca2+ are conserved in all six domains, the conserved glycine residues in the central portion of the EF-hand motif are absent in three of them. Calcium blots showed that recombinant reticulocalbin expressed in bacterial cells binds Ca2+. The protein has the sequence His-Asp-Glu-Leu (HDEL) at its carboxyl terminus. This is similar to the Lys-Asp-Glu-Leu sequence, which serves as a signal to retain the resident proteins in the endoplasmic reticulum of animal cells. A mutant protein lacking the HDEL sequence produced by in vitro mutagenesis has been shown to be secreted into medium in transient expression assays.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Binding Sites
  • Calbindins
  • Calcium-Binding Proteins / analysis
  • Calcium-Binding Proteins / genetics*
  • Calcium-Binding Proteins / metabolism*
  • Cloning, Molecular
  • DNA, Neoplasm / genetics
  • DNA, Neoplasm / isolation & purification
  • Endoplasmic Reticulum / metabolism*
  • Escherichia coli / genetics
  • Fluorescent Antibody Technique
  • Mice
  • Microsomes / metabolism
  • Molecular Sequence Data
  • Molecular Weight
  • Mutagenesis, Site-Directed
  • Oligodeoxyribonucleotides
  • Protein Conformation
  • Recombinant Proteins / analysis
  • Recombinant Proteins / metabolism
  • Restriction Mapping
  • S100 Calcium Binding Protein G / genetics
  • Teratoma
  • Tumor Cells, Cultured

Substances

  • Calbindins
  • Calcium-Binding Proteins
  • DNA, Neoplasm
  • Oligodeoxyribonucleotides
  • Recombinant Proteins
  • S100 Calcium Binding Protein G
  • reticulocalbin

Associated data

  • GENBANK/D13003