Salt bridge buried

Fig. 17. Models of A/ (l-40) fibrils, viewed down the fibril axis. (A, B) Cartoon representations of the hairpin model proposed by Petkova et al. (2002). (A) The proposed /1-strands span residues 9-24 and 30-40, with a main-chain bend spanning residues 25-29. Aspartate 23 and lysine 28 are proposed to form a salt bridge (dotted line) based on distance constraints provided by ssNMR. The hairpins stack in-register to form two parallel //-sheets. (B) Two hairpin stacks pack together to form the smallest observed fibrils, or protofilaments, burying the hydrophobic residues of the C-terminal strand. Two or more protofilaments may pack together to form thicker fibrils. (C) Cartoon representation of the parallel /i-helix-like model proposed byj. T. Guo and Y. Xu (unpublished model shown in Fig. 1 of Shivaprasad and Wetzel, 2004). The gray oval highlights residues 17 and 34, proposed to sit in close proximity.

Cavanagh, J., Venters, R.A. (2001) A structural double-mutant cycle estimating the strength of a buried salt bridge in barnase. Protein dynamic studies move to a new time slot, Nat. Struct. Biol. 8 (11), 912-914. 

Tissot, A. C., Vuilleumier, S., and Fersht, A. R. (1996) Importance of two buried salt bridges in the stability and folding pathway of bamase, Biochemistry 35, 6786-6794. 

Each interface contains 11 or 12 hydrogen bonds or salt bridge interactions. Although the GH/GHR complex buries more surface area into its interface, it stiU contains only 12 specific interactions. Three of the IFN-7/ IFN-7RI interactions occur between mainchain atoms in the AB loop of IFN-7 and the L2 loop of IFN-7RI. In addition to the 12 receptor-cytokine interactions, seven water molecules bridge the donor and acceptor groups of IFN-7 and IFN-7RI via hydrogen bonds (Randal and Kossiakoff, 2001). Since the B-factors for the water and protein atoms in the complex are essentially the same, the water molecules are considered to be an integral part of the interface. The presence of ordered water molecules in the IFN-7/IFN-7RI interface is not likely unique, since the IL-lO/IL-lORl interface is even more polar. However, the poorer diffraction quality of IL-10 complex crystals ( 2.9A versus 2.0A) obtained at this time prevents a detailed description of the interfacial waters. The water molecules in the... 

Two Buried Salt Bridges in the Stability and Folding Pathway of Barnase. 

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