Biosynthesis and mitochondrial processing of the beta subunit of propionyl coenzyme A carboxylase from rat liver.

J P Kraus,F Kalousek,L E Rosenberg

doi:10.1016/s0021-9258(18)32164-1

Abstract

Propionyl-CoA carboxylase (ADP-forming) (EC 6.4.1.3), an oligomer of nonidentical subunits (alpha 4 beta 4), has been localized to the mitochondrial matrix. As a first step in examining this enzyme's biogenesis, we have investigated in vitro the cell-free, rat liver RNA-directed synthesis of the beta subunit, and its post-translational transport and processing by rat liver mitochondria. The beta subunit is synthesized as a precursor approximately 7,500 daltons larger than its mature mitochondrial counterpart. The extension segment, comprising approximately 60 amino acids, is located at the NH2 terminus of the precursor. Intact mitochondria translocate the precursor across both mitochondrial membranes, and a protease localized to the mitochondrial matrix cleaves the precursor to a polypeptide identical in size and peptide composition to the mature beta subunit.

Highlights

We have begun to characterize the biogenesis of a second, compartmentalized,but more structurally complicated mitochondrialmatrix enzymep, ropionyl-CoA carboxylase
Propionyl-CoA carboxylase (ADP-forming) (EC are inherited in an autosomraelcessive fashion, itis clear that 6.4.1.3),an oligomer of nonidentical subunits (a4B4), the genetic loci coding for a and fl subunits arelocated in the has been localized to the mitochondrial matrix
As a nucleus.itfollows that first step in examining this enzyme’s biogenesis, we these polypeptides must be synthesized in the cytosol and have investigatedin vitro the cell-free,rat liver RNA- transportedacrossbothmitochondrialmembranestothe directed synthesis of the B subunit, and its post-trans- matrix

Summary

Introduction

We have begun to characterize the biogenesis of a second, compartmentalized,but more structurally complicated mitochondrialmatrix enzymep, ropionyl-CoA carboxylase Regions containing the precursor of the /j subunit of PCCase, itsmitochondrially processed form,andan authentic

Results

Conclusion