User:Katie Huff/Smaug Protein.
From Proteopedia
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Smaug Protein
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Smaug protein is involved with RNA-binding and translation inhibition. Specifically, Smaug is involved in anterior-posterior segmentation of the embryo during Drosophila melanogaster embryonic development. Smaug also plays a role in the midblastula transition of D. melanogaster development. 1 It is localized throughout the cytoplasm and pole plasm at the syncitial blastoderm stage. Later, during cellularization, it is most concentrated at the posterior pole. 2.
Function
Most eukaryotes rely on maternal mRNA in early development because they synthesize the proteins that control the primary events of embryogenesis (cell fate decisions, axis determination, etc.). Because maternal mRNAs are already present at the time of fertilization, their subsequent expression must be restricted post-transcriptionally 3. Smaug protein functions to regulate the posterior pole of the embryo by inhibiting translation of maternal nanos mRNA 1. Smaug effectively performs this task by binding to the 3'UTR region of the nanos mRNA via its sterile alpha motif (SAM) domain 2 This prevents nanos from passively diffusing to the posterior cortex of the embryo and undergoing translation. Smaug protein's mechanism of action involves the recruitment of another protein called CUP up binding to the 3'UTR region of nanos mRNA. Together, they prevent the association with a ribosome that would trigger translation. The nanos-Smaug-CUP complex can be undone, however, if the complex reaches the posterior cortex. In this case, the complex will be disassembled, which allows the mRNA to prepare its message for translation. In addition, Smaug is responsible for marking maternal mRNA for destruction in the mid-blastula transition. During this time, the embryo should begin a concomitant process called the maternal-to-zygotic transition. This process involves the degradation of maternal mRNA in favor of an increase in production of mRNA by the zygote 1.
Disease
Smaug is coded for by maternal mRNA, and its levels peak around the same time that the zygote can efficiently transcribe its genome. For maternal Smaug mutants, the mid-blastula and maternal-to-zygotic transitions will be hindered, and the zygotic genome transcription will ultimately be thwarted 1. Localization of nanos mRNA to the posterior cortex of the embryo is essential for proper development. Nanos protein is responsible for specifying the formation of the abdomen. If it is allowed to build up in the anterior cortex of the embryo, not only will it begin to specify abdominal precursors, but it will also suppress the development of the thorax and head of the embryo 3. This is a sample scene created with SAT to by Group, and another to make of the protein. You can make your own scenes on SAT starting from scratch or loading and editing one of these sample scenes.
About this Structure
1oxj is a 1 chain structure with sequence from D. melanogaster. Full crystallographic information is available from OCA.
Structure Reference
- Green JB, Gardner CD, Wharton RP, Aggarwal AK. RNA recognition via the SAM domain of Smaug. Mol Cell. 2003 Jun;11(6):1537-48. PMID:12820967
Text References
1 Gilbert, Scott F. Developmental Biology. 9th ed. Sunderland, MA: Sinauer Associates, 2006. p. 206;222. 2 "Protein Smaug - Smg - Drosophila Melanogaster (Fruit Fly)." UniProt. N.p., n.d. Last modified 16 Apr. 2014. 3 Andrews, S. et. al. (2011). "Multiple Mechanisms Collaborate to Repress Nanos Translation in the Drosophila Ovary and Embryo." RNA Society 17.5 (2011): 967-77.
