Investigating the protein-protein interactions of EccA3 in Mycobacterium smegmatis

Mycobacterium smegmatis encodes three ESX secretion systems, ESX-1, -3 and -4. Previous research has suggested localisation of the ESX-1 secretion system at the growing polar region of M. smegmatis. In a seperate study, we demonstrated unipolar localisation of EccA3 from ESX-3 at the growing polar region of M. smegmatis. Here we demonstrate that affinity purification of N-terminally FLAG-tagged MSMEG_0615 (EccA3) followed by mass spectrometry resulted in the co-purification proteins previously identified in the membrane fractions of M. tuberculosis. Furthermore, we demonstrate that EccA3 co-purified with proteins known to localise at the growing polar region of asymmetrically growing M. smegmatis, including Wag31 and CwsA.