Residues at the Cytoplasmic End of Transmembrane Helix 2 Determine the Signal Output of the Tar(Ec) Chemoreceptor

• Published in: Biochemistry (Easton) 2013-04, Vol.52 (16), p.2729
• Main Authors: Adase, Christopher A., Draheim, Roger R., Rueda, Garrett, Desai, Raj, Manson, Michael D.
• Format: Article
• Language: English
• ISSN: 1520-4995; 0006-2960
• DOI: 10.1021/bi4002002

Baseline signal output and communication between the periplasmic and cytoplasmic domains of the Escherichia colt aspartate chemoreceptor Tar(Ec) are both strongly influenced by residues at the C-terminus of transmembrane helix 2 (TM2). In particular, the cytoplasmic aromatic anchor, composed of residues Trp-209 and Tyr-210 in wild type Tar(Ec) is important for determining the CheA kinase-stimulating activity of the receptor and its ability to respond to chemoeffector-induced stimuli. Here, we have studied the effect on Tar(Ec) function of the six residue sequence at positions 207-212 Moving various combinations of aromatic residues among these positions generates substantial changes M receptor activity. Trp has the largest effect on function, both in maintaining normal activity and in altering activity when it is moved. Tyr has a weaker effect, and Phe has the weakest; however, all three aromatic residues can alter signal output when they are placed in novel positions. We also find that Gly-211 plays an important role in receptor function, perhaps because of the flexibility it introduces into the TM2-HAMP domain connector. The conservation of this Gly residue in the high-abundance chemoreceptors of E. coli and Salmonella enterica suggests that it may be important for the nuanced, bidirectional transmembrane signaling that occurs in these proteins.