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Structure of the newly found green turtle egg-white ribonuclease.

ABSTRACT: Marine green turtle (Chelonia mydas) egg-white ribonuclease (GTRNase) was crystallized from 1.1 M ammonium sulfate pH 5.5 and 30% glycerol using the sitting-drop vapour-diffusion method. The structure of GTRNase has been solved at 1.60 A resolution by the molecular-replacement technique using a model based on the structure of RNase 5 (murine angiogenin) from Mus musculus (46% identity). The crystal belonged to the monoclinic space group C2, with unit-cell parameters a = 86.271, b = 34.174, c = 39.738 A, alpha = 90, beta = 102, gamma = 90 degrees . GTRNase consists of three helices and seven beta-strands and displays the alpha+beta folding topology typical of a member of the RNase A superfamily. Superposition of the C(alpha) coordinates of GTRNase and RNase A superfamily members indicates that the overall structure is highly similar to that of angiogenin or RNase 5 from M. musculus (PDB code 2bwl) and RNase A from Bos taurus (PDB code 2blz), with root-mean-square deviations of 3.9 and 2.0 A, respectively. The catalytic residues are conserved with respect to the RNase A superfamily. The three disulfide bridges observed in the reptilian enzymes are conserved in GTRNase, while one further disulfide bond is required for the structural stability of mammalian RNases. GTRNase is expressed in egg white and the fact that its sequence has the highest similarity to that of snapping turtle pancreatic RNase suggests that the GTRNase secreted from oviduct cells to form egg white is probably the product of the same gene as activated in pancreatic cells.

SUBMITTER: Katekaew S

PROVIDER: S-EPMC2898455 | biostudies-literature | 2010 Jul

REPOSITORIES: biostudies-literature

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Structure of the newly found green turtle egg-white ribonuclease.

Katekaew Somporn S Kuaprasert Buabarn B Torikata Takao T Kakuta Yoshimitsu Y Kimura Makoto M Yoneda Kazunari K Araki Tomohiro T

Acta crystallographica. Section F, Structural biology and crystallization communications 20100623 Pt 7

Marine green turtle (Chelonia mydas) egg-white ribonuclease (GTRNase) was crystallized from 1.1 M ammonium sulfate pH 5.5 and 30% glycerol using the sitting-drop vapour-diffusion method. The structure of GTRNase has been solved at 1.60 A resolution by the molecular-replacement technique using a model based on the structure of RNase 5 (murine angiogenin) from Mus musculus (46% identity). The crystal belonged to the monoclinic space group C2, with unit-cell parameters a = 86.271, b = 34.174, c = 3 ...[more]

PMID: 20606267

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Project description:After gastrulation, oviductal hypoxia maintains turtle embryos in an arrested state prior to oviposition. Subsequent exposure to atmospheric oxygen upon oviposition initiates recommencement of embryonic development. Arrest can be artificially extended for several days after oviposition by incubation of the egg under hypoxic conditions, with development recommencing in an apparently normal fashion after subsequent exposure to normoxia. To examine the transcriptomic events associated with embryonic arrestAfter gastrulation, oviductal hypoxia maintains turtle embryos in an arrested state prior to oviposition. Subsequent exposure to atmospheric oxygen upon oviposition initiates recommencement of embryonic development. Arrest can be artificially extended for several days after oviposition by incubation of the egg under hypoxic conditions, with development recommencing in an apparently normal fashion after subsequent exposure to normoxia. To examine the transcriptomic events associated with embryonic arrest, RNA-sequencing analysis was performed on embryos from freshly laid eggs and eggs incubated in either normoxia (oxygen tension ~159 mmHg) or hypoxia (<8 mmHg) for 36 hours (h) after oviposition (n = 5 per group). The patterns of gene expression differed markedly among the three experimental groups. Normal embryonic development in normoxia was associated with up-regulation of genes involved in DNA replication, the cell cycle, and mitosis, but these genes were commonly down-regulated after incubation in hypoxia. Many target genes of hypoxia inducible factors, including insulin-like growth factor binding protein 1, were down-regulated by normoxic incubation but upregulated by incubation in hypoxia. Notably, some of the transcriptomic effects of hypoxia in green turtle embryos resembled those reported by others to be associated with hypoxia-induced embryonic arrest in diverse taxa, including budding yeast (Saccharomyces cerevisiae), the annelid Caenorhabditis elegans, and zebrafish (Danio rerio). Thus, while among oviparous species, hypoxia-induced pre-ovipositional embryonic arrest appears to be a unique adaptation of turtles, mechanisms underlying hypoxia-induced embryonic arrest per se may be highly conserved across the diverse taxa in which this mechanism operates. We report the transciptional changes in Chelonia mydas embryos incubated in either normoxia or hypoxia comapred to freshly laid eggs.

Dataset Information

Structure of the newly found green turtle egg-white ribonuclease.

Publications

Structure of the newly found green turtle egg-white ribonuclease.

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