How a Surface Protein Enables Metabolism of a Methane-Generating Microbe


Methanogenic microbes known as Archaea carry out many chemical transformations essential for anaerobic carbon recycling in virtually all environments. However, little is known about how raw materials for, and products of, these transformations are transported between an Archaeal cell and its environment. Research now has determined the structure of a key surface-layer protein of a methane-generating microbe, Methanosarcina acetivorans, enabling new insights into how this microbe communicates with its surroundings. The new information enables construction of a diagram of the cell envelope’s surface layer, showing the pores through which chemical species move back and forth. Three types of pores with distinctly different sizes and shapes were identified. All of them are small and highly negatively charged, which means that they are highly selective about which substances can pass through the layer into the cell. DNA sequencing of several related species of Methanosarcinales suggests that the structures of their surface layer proteins are similar to the one in M. acetivorans. These results provide valuable information for understanding the role of these microbes in producing methane in natural environments, a potentially major factor in global carbon cycling. The research was led by Robert Gunsalus of the UCLA-DOE Institute of Genomics and Proteomics.


Arbing, M. A., et al. 2012. “Structure of the Surface Layer of the Methanogenic Archaean Methanosarcina acetivorans,” Proceedings of the National Academy of Sciences of the USA 109(89), 11,812-817. DOI: 10.1073/pnas.1120595109.