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A globin domain in a neuronal transmembrane receptor of Caenorhabditis elegans and Ascaris suum: molecular modeling and functional properties.

ABSTRACT: We report the structural and biochemical characterization of GLB-33, a putative neuropeptide receptor that is exclusively expressed in the nervous system of the nematode Caenorhabditis elegans. This unique chimeric protein is composed of a 7-transmembrane domain (7TM), GLB-33 7TM, typical of a G-protein-coupled receptor, and of a globin domain (GD), GLB-33 GD. Comprehensive sequence similarity searches in the genome of the parasitic nematode, Ascaris suum, revealed a chimeric protein that is similar to a Phe-Met-Arg-Phe-amide neuropeptide receptor. The three-dimensional structures of the separate domains of both species and of the full-length proteins were modeled. The 7TM domains of both proteins appeared very similar, but the globin domain of the A. suum receptor surprisingly seemed to lack several helices, suggesting a novel truncated globin fold. The globin domain of C. elegans GLB-33, however, was very similar to a genuine myoglobin-type molecule. Spectroscopic analysis of the recombinant GLB-33 GD showed that the heme is pentacoordinate when ferrous and in the hydroxide-ligated form when ferric, even at neutral pH. Flash-photolysis experiments showed overall fast biphasic CO rebinding kinetics. In its ferrous deoxy form, GLB-33 GD is capable of reversibly binding O2 with a very high affinity and of reducing nitrite to nitric oxide faster than other globins. Collectively, these properties suggest that the globin domain of GLB-33 may serve as a highly sensitive oxygen sensor and/or as a nitrite reductase. Both properties are potentially able to modulate the neuropeptide sensitivity of the neuronal transmembrane receptor.

SUBMITTER: Tilleman L

PROVIDER: S-EPMC4400345 | biostudies-literature | 2015 Apr

REPOSITORIES: biostudies-literature

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A globin domain in a neuronal transmembrane receptor of Caenorhabditis elegans and Ascaris suum: molecular modeling and functional properties.

Tilleman Lesley L Germani Francesca F De Henau Sasha S Helbo Signe S Desmet Filip F Berghmans Herald H Van Doorslaer Sabine S Hoogewijs David D Schoofs Liliane L Braeckman Bart P BP Moens Luc L Fago Angela A Dewilde Sylvia S

The Journal of biological chemistry 20150209 16

We report the structural and biochemical characterization of GLB-33, a putative neuropeptide receptor that is exclusively expressed in the nervous system of the nematode Caenorhabditis elegans. This unique chimeric protein is composed of a 7-transmembrane domain (7TM), GLB-33 7TM, typical of a G-protein-coupled receptor, and of a globin domain (GD), GLB-33 GD. Comprehensive sequence similarity searches in the genome of the parasitic nematode, Ascaris suum, revealed a chimeric protein that is sim ...[more]

PMID: 25666609

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Project description:The nucleotide sequences of the mitochondrial DNA (mtDNA) molecules of two nematodes, Caenorhabditis elegans [13,794 nucleotide pairs (ntp)], and Ascaris suum (14,284 ntp) are presented and compared. Each molecule contains the genes for two ribosomal RNAs (s-rRNA and l-rRNA), 22 transfer RNAs (tRNAs) and 12 proteins, all of which are transcribed in the same direction. The protein genes are the same as 12 of the 13 protein genes found in other metazoan mtDNAs: Cyt b, cytochrome b; COI-III, cytochrome c oxidase subunits I-III; ATPase6, Fo ATPase subunit 6; ND1-6 and 4L, NADH dehydrogenase subunits 1-6 and 4L: a gene for ATPase subunit 8, common to other metazoan mtDNAs, has not been identified in nematode mtDNAs. The C. elegans and A. suum mtDNA molecules both include an apparently noncoding sequence that contains runs of AT dinucleotides, and direct and inverted repeats (the AT region: 466 and 886 ntp, respectively). A second, apparently noncoding sequence in the C. elegans and A. suum mtDNA molecules (109 and 117 ntp, respectively) includes a single, hairpin-forming structure. There are only 38 and 89 other intergenic nucleotides in the C. elegans and A. suum mtDNAs, and no introns. Gene arrangements are identical in the C. elegans and A. suum mtDNA molecules except that the AT regions have different relative locations. However, the arrangement of genes in the two nematode mtDNAs differs extensively from gene arrangements in all other sequenced metazoan mtDNAs. Unusual features regarding nematode mitochondrial tRNA genes and mitochondrial protein gene initiation codons, previously described by us, are reviewed. In the C. elegans and A. suum mt-genetic codes, AGA and AGG specify serine, TGA specifies tryptophan and ATA specifies methionine. From considerations of amino acid and nucleotide sequence similarities it appears likely that the C. elegans and A. suum ancestral lines diverged close to the time of divergence of the cow and human ancestral lines, about 80 million years ago.

Project description:The nematode intestine is a major organ responsible for nutrient digestion and absorption; it is also involved in many other processes, such as reproduction, innate immunity, stress responses, and aging. The importance of the intestine as a target for the control of parasitic nematodes has been demonstrated. However, the lack of detailed knowledge on the molecular and cellular functions of the intestine and the level of its conservation across nematodes has impeded breakthroughs in this application.As part of an extensive effort to investigate various transcribed genomes from Ascaris suum and Haemonchus contortus, we generated a large collection of intestinal sequences from parasitic nematodes by identifying 3,121 A. suum and 1,755 H. contortus genes expressed in the adult intestine through the generation of expressed sequence tags. Cross-species comparisons to the intestine of the free-living C. elegans revealed substantial diversification in the adult intestinal transcriptomes among these species, suggesting lineage- or species-specific adaptations during nematode evolution. In contrast, significant conservation of the intestinal gene repertories was also evident, despite the evolutionary distance of approximately 350 million years separating them. A group of 241 intestinal protein families (IntFam-241), each containing members from all three species, was identified based on sequence similarities. These conserved proteins accounted for approximately 20% of the sampled intestinal transcriptomes from the three nematodes and are proposed to represent conserved core functions in the nematode intestine. Functional characterizations of the IntFam-241 suggested important roles in molecular functions such as protein kinases and proteases, and biological pathways of carbohydrate metabolism, energy metabolism, and translation. Conservation in the core protein families was further explored by extrapolating observable RNA interference phenotypes in C. elegans to their parasitic counterparts.Our study has provided novel insights into the nematode intestine and lays foundations for further comparative studies on biology, parasitism, and evolution within the phylum Nematoda.

Dataset Information

A globin domain in a neuronal transmembrane receptor of Caenorhabditis elegans and Ascaris suum: molecular modeling and functional properties.

Publications

A globin domain in a neuronal transmembrane receptor of Caenorhabditis elegans and Ascaris suum: molecular modeling and functional properties.

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