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Signal transduction in the archaeon Halobacterium salinarium is processed through three subfamilies of 13 soluble and membrane-bound transducer proteins.

ABSTRACT: Eubacterial transducers are transmembrane, methyl-accepting proteins central to chemotaxis systems and share common structural features. We identified a large family of transducer proteins in the Archaeon Halobacterium salinarium using a site-specific multiple antigenic peptide antibody raised against 23 amino acids, representing the highest homology region of eubacterial transducers. This immunological observation was confirmed by isolating 13 methyl-accepting taxis genes using a 27-mer oligonucleotide probe, corresponding to conserved regions between the eubacterial and first halobacterial phototaxis transducer gene htrI. On the basis of the comparison of the predicted structural domains of these transducers, we propose that at least three distinct subfamilies of transducers exist in the Archaeon H. salinarium: (i) a eubacterial chemotaxis transducer type with two hydrophobic membrane-spanning segments connecting sizable domains in the periplasm and cytoplasm; (ii) a cytoplasmic domain and two or more hydrophobic transmembrane segments without periplasmic domains; and (iii) a cytoplasmic domain without hydrophobic transmembrane segments. We fractionated the halobacterial cell lysate into soluble and membrane fractions and localized different halobacterial methyl-accepting taxis proteins in both fractions.

SUBMITTER: Zhang W

PROVIDER: S-EPMC39333 | biostudies-other | 1996 May

REPOSITORIES: biostudies-other

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Signal transduction in the archaeon Halobacterium salinarium is processed through three subfamilies of 13 soluble and membrane-bound transducer proteins.

Zhang W W Brooun A A McCandless J J Banda P P Alam M M

Proceedings of the National Academy of Sciences of the United States of America 19960501 10

Eubacterial transducers are transmembrane, methyl-accepting proteins central to chemotaxis systems and share common structural features. We identified a large family of transducer proteins in the Archaeon Halobacterium salinarium using a site-specific multiple antigenic peptide antibody raised against 23 amino acids, representing the highest homology region of eubacterial transducers. This immunological observation was confirmed by isolating 13 methyl-accepting taxis genes using a 27-mer oligonu ...[more]

PMID: 8643458

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Project description:Recently, a large family of transducer proteins in the Archaeon Halobacterium salinarium was identified. On the basis of the comparison of the predicted structural domains of these transducers, three distinct subfamilies of transducers were proposed. Here we report isolation, complete gene sequences, and analysis of the encoded primary structures of transducer gene htrII, a member of family B, and its blue light receptor gene (sopII) of sensory rhodopsin II (SRII). The start codon ATG of the 714-bp sopII gene is one nucleotide beyond the termination codon TGA of the 2298-bp htrII gene. The deduced protein sequence of HtrII predicts a eubacterial chemotaxis transducer type with two hydrophobic membrane-spanning segments connecting sizable domains in the periplasm and cytoplasm. HtrII has a common feature with HtrI, the sensory rhodopsin I transducer; like HtrI, HtrII possesses a hydrophilic loop structure just after the second transmembrane segment. The C-terminal 299 residues (765 amino acid residues total) of HtrII show strong homology to the signaling and methylation domain of eubacterial transducer Tsr. The hydropathy plot of the primary structure of SRII indicates seven membrane-spanning alpha-helical segments, a characteristic feature of retinylidene proteins ("rhodopsins") from a widespread family of photoactive pigments. SRII shows high identity with SRI (42%), bacteriorhodopsin (BR) (32%), and halorhodopsin (24%). The crucial positions for retinal binding sites in these proteins are nearly identical, with the exception of Met-118 (numbering according to the mature BR sequence), which is replaced by Val in SRII. In BR, residues Asp-85 and Asp-96 are crucial in proton pumping. In SRII, the position corresponding to Asp-85 in BR is conserved, but the corresponding position of Asp-96 is replaced by an aromatic Tyr. Coexpression of the htrII and sopII genes restores SRII phototaxis to a mutant (Pho81) that contains a deletion in the htrI/sopI and insertion in htrII/sopII regions. This paper describes the first example that both HtrI and HtrII exist in the same halobacterial cell, confirming that different sensory rhodopsins SRI and SRII in the same organism have their own distinct transducers.

Dataset Information

Signal transduction in the archaeon Halobacterium salinarium is processed through three subfamilies of 13 soluble and membrane-bound transducer proteins.

Publications

Signal transduction in the archaeon Halobacterium salinarium is processed through three subfamilies of 13 soluble and membrane-bound transducer proteins.

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