The HAMP linker domain (domain present in Histidine kinases, Adenyl cyclases, Methyl-accepting proteins and Phosphatases) is an approximately 50-amino acid α-helical region common to chemoreceptors and histidine kinases that is present in several multidomain sensor proteins that participate in a variety of signal transduction processes. One or several copies of the HAMP domain can be found in association with other domains such as the histidine kinase domain (see <PDOC50109>), the bacterial chemotaxis sensory transducer domain (see <PDOC00465>), the PAS repeat (see <PDOC50112>), the EAL domain (see <PDOC50883>), the GGDEF domain (see <PDOC50887>), the protein phosphatase 2C-like domain, the guanylate cyclase domain (see <PDOC00425>), or the response regulatory domain (see <PDOC50110>). It has been suggested that the HAMP domain possesses a role of regulating the phosphorylation or methylation of homodimeric receptors by transmitting the conformational changes in periplasmic ligand-binding domains to cytoplasmic signalling kinase and methyl-acceptor domains [1].

Some proteins known to contain a HAMP domain are listed below:

• Anabaena cylindrica adenylate cyclase. It may function as a membrane- localized receptor protein.
• Escherichia coli osmolarity sensor protein envZ. It functions as a membrane-associated protein kinase that phosphorylates ompR in response to environmental signals.
• Escherichia coli sensor protein barA. It could activate ompR by phosphorylation.
• Escherichia coli nitrate/nitrite sensor protein narX. It probably activates narL and narP by phosphorylation in the presence of nitrate.
• Escherichia coli sensor protein cpxA.
• Escherichia coli methyl-accepting chemotaxis protein I.
• Escherichia coli hypothetical protein yfiN.
• Escherichia coli protein yhjK.
• Rhizobium sp. strain NGR234 probable chemoreceptor Y4FA.
• Salmonella typhimurium methyl-accepting chemotaxis protein II.
• Chlamydia trachomatis sigma regulatory family protein-PP2C phosphatase.
• Treponema pallidum hypothetical protein TP0854.
• Synechocystis sp. strain PCC 6803 pleD.
• Synechocystis sp. strain PCC 6803 hypothetical protein sll1365.
• Archaeoglobus fulgidus putative signal-transducing histidine kinase.
• Archaeoglobus fulgidus hypothetical protein AF1503.
• Halobacterium salinarium halobacterial transducer protein IV.
• Yeast osmolarity two-component system protein SLN1.
• Candida albicans protein NIK1.

The profile we developed covers the entire HAMP domain.