Methanobactin MbnE, a periplasmic binding protein of the TonB-dependent transport system, and similar proteins.
Methanobactin MbnE is a periplasmic binding protein that is involved in the TonB-dependent transport system in bacteria. The function of MbnE is to bind to methanobactin and transport it across the periplasmic space to the TonB receptor on the outer membrane of the cell. The binding of MbnE to methanobactin allows the bacteria to scavenge iron from the environment, which is essential for many biological processes. The evolutionary relationship between MbnE and the ABC transport system is not clear, as they are distinct systems that have evolved separately. However, it is possible that there have been some functional convergences between these systems in terms of nutrient uptake and transport.