Classification and Organisation of Two-component Systems
David E. Whitworth
from: Two-Component Systems in Bacteria (Edited by: Roy Gross and Dagmar Beier). Caister Academic Press, U.K. (2012)
Two-component systems (TCSs) are common signal transduction pathways found abundantly in most phyla except animals. The basic TCS pathway involves two multi-domain proteins. The first is a histidine protein kinase (HPK) whose autokinase activity is dependent upon an environmental stimulus. The second is a response regulator (RR), onto which a phosphoryl group is transferred from the phosphorylated HPK, and which mediates phosphorylation-dependent effects within the cell. TCS proteins can be readily identified from genomic sequences, however, approaches for identifying and classifying TCS proteins are non-trivial because TCSs are multi-domain, multi-gene pathways, which exhibit considerable heterogeneity in their gene and domain organisation. This chapter provides an overview of the domain architectures and genetic organisation of TCSs, including the common TCS variants known as phosphorelays and chemosensory systems. Strategies for the identification of TCS genes are described, alongside systems for categorising TCS proteins that exploit the evolutionary relationships between TCS proteins to provide biologically relevant insights. The development of such classification systems are reviewed in addition to the current state of the art, to help the reader navigate through the extensive literature on this topic read more ...