The gene ipdA (REQ_07170) is an ortholog of rv3551 of Mycobacterium tuberculosis and likewise localized in the cholesterol catabolic gene cluster of its bacterial chromosome of Rhodococcus equi. The encoded protein IpdA (GenBank accession CBH46834) carries the PF01144 signature motif of heterodimeric coenzyme A transferase as well as the COG1788 signature of AtoD, the alpha subunit acetoacetyl-CoA transferase of E. coli. It is thought that IpdA is an alpha subunit of a heterodimeric coenzyme A transferase involved in steroid catabolism, more specific in methylhexahydroindanone propionate degradation. It was shown that the cholesterol catabolism is important for pathogenicity of R. equi.