3ua0

N-Terminal Domain of Bombyx mori Fibroin Mediates the Assembly of Silk in Response to pH Decrease

spinqualitylabelsall models 3ua0, resolution 3.00Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 3ua0 is a 2 chain structure with sequence from Bommo. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. NonStd Res: MSE Gene: FIBH (BOMMO) Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function [FIBH_BOMMO] Core component of the silk filament; a strong, insoluble and chemically inert fiber. Publication Abstract from PubMed Fibroins serve as the major building blocks of silk fiber. As the major component of fibroin, the fibroin heavy chain is a considerably large protein comprising N-terminal and C-terminal hydrophilic domains and 12 highly repetitive Gly-Ala-rich regions flanked by internal hydrophilic blocks. Here, we show the crystal structure of the fibroin N-terminal domain (FibNT) at pH 4.7, revealing a remarkable double-layered anti-parallel beta-sheet with each layer comprising two FibNT molecules entangled together. We also show that FibNT undergoes a pH-responsive conformational transition from random coil to beta-sheets at around pH 6.0. Dynamic light scattering demonstrates that FibNT tends to oligomerize as pH decreases to 6.0, and electron microscopy reveals micelle-like oligomers. Our results are consistent with the micelle assembly model of silk fibroin and, more importantly, show that the N-terminal domain in itself has the capacity to form micelle-like structures in response to pH decrease. Structural and mutagenesis analyses further reveal the important role of conserved acidic residues clustered in FibNT, such as Glu56 and Asp100, in preventing premature beta-sheet formation at neutral pH. Collectively, we suggest that FibNT functions as a pH-responsive self-assembly module that could prevent premature beta-sheet formation at neutral pH yet could initiate fibroin assembly as pH decreases along the lumen of the posterior silk gland to the anterior silk gland. N-Terminal Domain of Bombyx mori Fibroin Mediates the Assembly of Silk in Response to pH Decrease.,He YX, Zhang NN, Li WF, Jia N, Chen BY, Zhou K, Zhang J, Chen Y, Zhou CZ J Mol Biol. 2012 Mar 1. PMID:22387468 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Fibroins

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