Dataset Information

Ectodomain Architecture Affects Sequence and Functional Evolution of Vertebrate Toll-like Receptors.

ABSTRACT: Toll-like receptors (TLRs) are crucial components of innate immunity that specifically recognize diverse pathogen-associated molecular patterns from pathogens. The continuous hydrogen-bond network (asparagine ladder) formed among the asparagine residues on the concave surfaces of neighboring leucine-rich repeat modules assists in stabilizing the overall shape of TLR ectodomains responsible for ligand recognition. Analysis of 28 types of vertebrate TLRs showed that their ectodomains possessed three types of architectures: a single-domain architecture with an intact asparagine ladder, a three-domain architecture with the ladder interrupted in the middle, and a trans-three-domain architecture with the ladder broken in both termini. Based on a phylogenetic analysis, the three vertebrate TLR architectures arose during early evolution. The 1428 vertebrate TLRs can be divided into eight families based on sequence and structural differences. TLRs ligand specificities are affected by their ectodomain architectures. Three-domain TLRs bind hydrophobic ligands, whereas single-domain and trans-three-domain TLRs mainly recognize hydrophilic ligands. Analysis of 39 vertebrate genomes suggested that the number of single-domain TLR genes in terrestrial vertebrate genomes decreased by half compared to aquatic vertebrate genomes. Single-domain TLR genes underwent stronger purifying selective pressures than three-domain TLR genes in mammals. Overall, ectodomain architecture influences the sequence and functional evolution of vertebrate TLRs.

SUBMITTER: Wang J

PROVIDER: S-EPMC4877655 | biostudies-literature | 2016 May

REPOSITORIES: biostudies-literature

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Ectodomain Architecture Affects Sequence and Functional Evolution of Vertebrate Toll-like Receptors.

Wang Jinlan J Zhang Zheng Z Liu Jing J Zhao Jing J Yin Deling D

Scientific reports 20160524

Toll-like receptors (TLRs) are crucial components of innate immunity that specifically recognize diverse pathogen-associated molecular patterns from pathogens. The continuous hydrogen-bond network (asparagine ladder) formed among the asparagine residues on the concave surfaces of neighboring leucine-rich repeat modules assists in stabilizing the overall shape of TLR ectodomains responsible for ligand recognition. Analysis of 28 types of vertebrate TLRs showed that their ectodomains possessed thr ...[more]

PMID: 27216145

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Project description:BACKGROUND: Toll-like receptors (TLRs) play a central role in innate immunity. TLRs are membrane glycoproteins and contain leucine rich repeat (LRR) motif in the ectodomain. TLRs recognize and respond to molecules such as lipopolysaccharide, peptidoglycan, flagellin, and RNA from bacteria or viruses. The LRR domains in TLRs have been inferred to be responsible for molecular recognition. All LRRs include the highly conserved segment, LxxLxLxxNxL, in which "L" is Leu, Ile, Val, or Phe and "N" is Asn, Thr, Ser, or Cys and "x" is any amino acid. There are seven classes of LRRs including "typical" ("T") and "bacterial" ("S"). All known domain structures adopt an arc or horseshoe shape. Vertebrate TLRs form six major families. The repeat numbers of LRRs and their "phasing" in TLRs differ with isoforms and species; they are aligned differently in various databases. We identified and aligned LRRs in TLRs by a new method described here. RESULTS: The new method utilizes known LRR structures to recognize and align new LRR motifs in TLRs and incorporates multiple sequence alignments and secondary structure predictions. TLRs from thirty-four vertebrate were analyzed. The repeat numbers of the LRRs ranges from 16 to 28. The LRRs found in TLRs frequently consists of LxxLxLxxNxLxxLxxxxF/LxxLxx ("T") and sometimes short motifs including LxxLxLxxNxLxxLPx(x)LPxx ("S"). The TLR7 family (TLR7, TLR8, and TLR9) contain 27 LRRs. The LRRs at the N-terminal part have a super-motif of STT with about 80 residues. The super-repeat is represented by STTSTTSTT or _TTSTTSTT. The LRRs in TLRs form one or two horseshoe domains and are mostly flanked by two cysteine clusters including two or four cysteine residue. CONCLUSION: Each of the six major TLR families is characterized by their constituent LRR motifs, their repeat numbers, and their patterns of cysteine clusters. The central parts of the TLR1 and TLR7 families and of TLR4 have more irregular or longer LRR motifs. These central parts are inferred to play a key role in the structure and/or function of their TLRs. Furthermore, the super-repeat in the TLR7 family suggests strongly that "bacterial" and "typical" LRRs evolved from a common precursor.

Dataset Information

Ectodomain Architecture Affects Sequence and Functional Evolution of Vertebrate Toll-like Receptors.

Publications

Ectodomain Architecture Affects Sequence and Functional Evolution of Vertebrate Toll-like Receptors.

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