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Title
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A globin domain in a neuronal transmembrane receptor of **Caenorhabditis elegans** and **Ascaris suum** : molecular modeling and functional properties
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Author
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Abstract
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| 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, GLB-33 7TM, typical of a G-protein-coupled receptor, and of a globin domain, 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 globin domain 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. |
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Language
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English
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Source (journal)
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Journal of biological chemistry. - Baltimore, Md
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Publication
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Baltimore, Md
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2015
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ISSN
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0021-9258
[print]
1083-351X
[online]
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DOI
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10.1074/JBC.M114.576520
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Volume/pages
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290
:16
(2015)
, p. 10336-10352
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ISI
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000353241100036
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Full text (Publisher's DOI)
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Full text (open access)
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Full text (publisher's version - intranet only)
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