Holocarboxylase synthetase: correlation of protein localisation with biological function

Arch Biochem Biophys. 2010 Apr 1;496(1):45-52. doi: 10.1016/j.abb.2010.01.015. Epub 2010 Feb 11.

Abstract

Holocarboxylase synthetase (HCS) governs the cellular fate of the essential micronutrient biotin (Vitamin H or B7). HCS is responsible for attaching biotin onto the biotin-dependent enzymes that reside in the cytoplasm and mitochondria. Evidence for an alternative role, viz the regulation of gene expression, has also been reported. Recent immunohistochemical studies reported HCS is primarily nuclear, inconsistent with the location of HCS activity. Improved understanding of biotin biology demands greater knowledge about HCS. Here, we investigated the localisation of HCS and its isoforms. Three variants were observed that differ at the N-terminus. All HCS isoforms were predominantly non-nuclear, consistent with the distribution of biotin protein ligase activity. Unlike the longer constructs, the Met(58) isoform was also detected in the nucleus--a novel observation suggesting shuttling activity between nucleus and cytoplasm. We resolved that the previous controversies in the literature are due to specificity and detection limitations that arise when using partially purified antibodies.

MeSH terms

  • Animals
  • Carbon-Nitrogen Ligases / immunology
  • Carbon-Nitrogen Ligases / metabolism*
  • Computational Biology
  • Fluorescent Antibody Technique
  • HeLa Cells
  • Humans
  • Immune Sera / immunology
  • Intracellular Space / metabolism
  • Isoenzymes / immunology
  • Isoenzymes / metabolism
  • Protein Transport
  • Recombinant Fusion Proteins / immunology
  • Recombinant Fusion Proteins / metabolism

Substances

  • Immune Sera
  • Isoenzymes
  • Recombinant Fusion Proteins
  • Carbon-Nitrogen Ligases
  • holocarboxylase synthetases