Abstract
Biotin-mediated carboxylation of short-chain fatty acid coenzyme A esters is a key step in lipid biosynthesis that is carried out by multienzyme complexes to extend fatty acids by one methylene group. Pathogenic mycobacteria have an unusually high redundancy of carboxyltransferase genes and biotin carboxylase genes, creating multiple combinations of protein/protein complexes of unknown overall composition and functional readout. By combining pull-down assays with mass spectrometry, we identified nine binary protein/protein interactions and four validated holo acyl-coenzyme A carboxylase complexes. We investigated one of these - the AccD1-AccA1 complex from Mycobacterium tuberculosis with hitherto unknown physiological function. Using genetics, metabolomics and biochemistry we found that this complex is involved in branched amino-acid catabolism with methylcrotonyl coenzyme A as the substrate. We then determined its overall architecture by electron microscopy and found it to be a four-layered dodecameric arrangement that matches the overall dimensions of a distantly related methylcrotonyl coenzyme A holo complex. Our data argue in favor of distinct structural requirements for biotin-mediated γ-carboxylation of α−β unsaturated acid esters and will advance the categorization of acyl-coenzyme A carboxylase complexes. Knowledge about the underlying structural/functional relationships will be crucial to make the target category amenable for future biomedical applications.
Highlights
Biotin-dependent acyl-CoA carboxylases (YCCs) are ubiquitous multifunctional enzymes that are found in all kingdoms of life
This pathogen has a complex metabolism with many genes required for the synthesis of components of its unique cell envelope
We have investigated a family of closely related genes coding for different acyl CoA carboxylase enzyme complexes with previously unexplained genetic redundancy that have been thought to have an involvement in the synthesis of these cell envelope components
Summary
Biotin-dependent acyl-CoA carboxylases (YCCs) are ubiquitous multifunctional enzymes that are found in all kingdoms of life. They have key roles in the metabolism of fatty acids, amino acids, and carbohydrates and have various, more specialized functions in microorganisms [1,2]. The reaction schemes of the YCCs all have two sequential steps in common: first, the biotin post-translationally attached to a biotin carboxyl carrier protein (BCCP) is carboxylated in an ATP-dependent manner by a biotin carboxylase (BC); second, carboxybiotin attached to the BCCP is transferred to the active site of the carboxyltransferase (CT), where the transfer of the carboxyl group from biotin to the acylCoA substrate takes place to extend the acyl-CoA by one carboxyl group. One of the reasons for this lack of progress is that there is no structural and functional repository of all mycobacterial YCC complexes, which would allow the development of specific approaches against individual members
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
