Mitochondrial targeting signals and mature peptides of 3-methylcrotonyl-CoA carboxylase

Biochem Biophys Res Commun. 2005 Sep 2;334(3):939-46. doi: 10.1016/j.bbrc.2005.06.190.


Inherited deficiency of 3-methylcrotonyl-CoA carboxylase (MCC), an enzyme of leucine degradation, is an organic acidemia detectable by expanded newborn screening with a variable phenotype that ranges from asymptomatic to death in infancy. Here, we show that the two subunits of the enzyme (MCCalpha; MCCbeta) are imported into the mitochondrial matrix by the classical pathway involving cleavable amino-terminal targeting presequences. We identified the cleavage sites (Tyr41/Thr42 and Ala22/Tyr23 for MCCalpha and MCCbeta, respectively) of the targeting signals and the amino-termini of the mature polypeptides of MCC and propionyl-CoA carboxylase, a mitochondrial paralog. The amino-termini containing 39 (MCCalpha) or 20 amino acids (MCCbeta) were both necessary and sufficient for targeting. Structural requirements for mitochondrial import were defined by site-directed mutagenesis. Our studies provide the prerequisite to understand the impact of specific mutations on the clinical phenotype of MCC deficiency.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Carbon-Carbon Ligases / chemistry
  • Carbon-Carbon Ligases / deficiency
  • Carbon-Carbon Ligases / genetics
  • Carbon-Carbon Ligases / metabolism*
  • Carrier Proteins / metabolism
  • Humans
  • Kidney / chemistry
  • Mitochondria / metabolism*
  • Molecular Sequence Data
  • Protein Transport / physiology*
  • Recombinant Fusion Proteins / metabolism
  • Saccharomyces cerevisiae / metabolism


  • Carrier Proteins
  • Recombinant Fusion Proteins
  • biotin-binding proteins
  • Carbon-Carbon Ligases
  • propionyl CoA carboxylase (ATP-hydrolyzing)
  • methylcrotonoyl-CoA carboxylase