Mycobacterium tuberculosis Rv1916 is an Acetyl-CoA-Binding Protein

Isocitrate lyase (ICL) isoform 2 is an essential enzyme for some clinical Mycobacterium tuberculosis (Mtb) strains during infection. In the laboratory Mtb strain H37Rv, the icl2 gene encodes two distinct gene products - Rv1915 and Rv1916 - due to a frameshift mutation. This study aims to characterise these two gene products to understand their structure and function. While we were unable to produce Rv1915 recombinantly, soluble Rv1916 was obtained with sufficient yield for characterisation. Kinetic studies using UV-visible spectrophotometry and H-1-NMR spectroscopy showed that recombinant Rv1916 does not possess isocitrate lyase activity, while waterLOGSY binding experiments demonstrated that it could bind acetyl-CoA. Finally, X-ray crystallography revealed structural similarities between Rv1916 and the C-terminal domain of ICL2. Considering the probable differences between full-length ICL2 and the gene products Rv1915 and Rv1916, care must be taken when using Mtb H37Rv as a model organism to study central carbon metabolism.

Automated summary

The icl2 gene in Mycobacterium tuberculosis strain H37Rv encodes two different products, Rv1915 and Rv1916, due to a frameshift mutation. While Rv1916 shows structural similarities to the C-terminal domain of ICL2 and can bind acetyl-CoA, it lacks isocitrate lyase activity. Caution should be exercised when using Mtb H37Rv as a model organism for studying central carbon metabolism due to potential differences between full-length ICL2 and the gene products Rv1915 and Rv1916.