Mitochondrial targeting signals and mature peptides of 3-methylcrotonyl-CoA carboxylase.
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.
Stadler
Sonja C
SC
Dr. von Hauner Children's Hospital, Department of Biochemical Genetics and Molecular Biology, Ludwig-Maximilians-University, Munich, Germany.
Polanetz
Roman
R
Meier
Stephan
S
Mayerhofer
Peter U
PU
Herrmann
Johannes M
JM
Anslinger
Katja
K
Roscher
Adelbert A
AA
Röschinger
Wulf
W
Holzinger
Andreas
A
D000595:Amino Acid Sequence; D019735:Carbon-Carbon Ligases / Q000737:chemistry / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism; D006801:Humans; D007668:Kidney / Q000737:chemistry; D008928:Mitochondria / Q000378:metabolism*; D008969:Molecular Sequence Data; D021381:Protein Transport / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000378:metabolism
D002352:Carrier Proteins; D011993:Recombinant Fusion Proteins; C017071:biotin-binding proteins; D019735:Carbon-Carbon Ligases; C022458:propionyl CoA carboxylase (ATP-hydrolyzing); C021573:methylcrotonoyl-CoA carboxylase