B-strands

Very recently 13 the three dimensional structure of the CBH II core was fully determined by X-ray diffraction. The polypeptide chain is folded in a-helices and B-strands (a,B-protein with a central B-barrel built up by seven parallel strands. Six of the )3-strands are linked by a-helices. Near the C-terminus of the enzyme is a tunnel with dimensions well suited to take up a single cellulose chain. Two aspartic acid residues (175 and 221) are probably involved in the active center. 

Figure 9.7 If adopting an extended conformation, (a) strands 10 and 11 should form H bonded polymer chains, (b) strands 10 and 11 should form an 8-H bonded duplex, and (c) strand 12 should form H bonded polymer chains.

Reactions catalyzed by purified recA protein in vitro. RecA catalyzes a number of different reactions between DNA strands, all of them involving the unwinding and winding of base-paired structures, (a) D-loop formation by interaction between supercoiled circular duplex DNA and single-stranded DNA. (b) Strand exchange between a gapped circular duplex structure and a linear duplex structure, (c) Complex formation between two helices, one of which is gapped. 

The Rieske protein has an N-terminal membrane anchor followed by a C-tenninal water soluble domain of approximately 14 kDa between diese two elements, there is a 12-residue flexible linker which allows movement of the water soluble domain (see section 3.3.1). The folding of the water soluble domain is the Rieske fold consisting of three antiparallel B-sheets [21]. Sheet 3 is formed by the B strands B5 - B8 these strands and the loops connecting them form die cluster binding subdomain comprising 44 residues. 

In the past few years, crystal structmes have been published of three of the seven outer-membrane-siderophore receptors from E.coli, namely of FepA,FhuA, and FecA. FepA and FhuA represent similar monomeric transmembrane proteins that are composed of 22 antiparallel B-strands of approximately 70 A height (Figme 11). The right-handed twist of the /3-strands produces an ellipticalshaped barrel with a diameter of 35 x 47 A constituting a transmembrane pore. Targe extracellular loops extend... 

For a romantic evening try B.B. Strand s (310 N. 4th St., rr 208-342-3777), located in an old 1929 grocery store with plenty of character. The Vegetable Wellington - grilled vegetables and cheese in a rich mushroom sauce wrapped in a pastry - is a fixture on its menu. 

Hampson AJ, Grimaldi M, Axelrod J, Wink D (1998) Cannabidiol and (-)delta9-tetrahydro-cannabinol are neuroprotective antioxidants. Proc Natl Acad Sci USA 95 8268-8273 Hansen HS,Lauritzen L, Moesgaard B, Strand AM, Hansen HH (1998) Formation ofN-acyl-... 

Zhang, S. and Egli, M. (1995). A proposed complementary pairing mode between single-stranded nucleic acids and b-stranded peptides a possible pathway for generating complex biological molecules. Complexity, 1, 49-56. 

Wieczorek, R., and Dannenberg, J. J. (2004) Comparison of fully optimized a-and 3.10-Helices with extended b-strands. An ONIOM density functional theory study. J.Am. Chem. Soc. 126, 14198-14205. 

The linear peptide as observed in its primary structure starts folding on itself because of the interactions among the side chains of the adjacent amino acids. This leads to the formation of different structures, which include (a) helical structure called an alpha helix, (b) stranded folds called beta sheets or beta strands, and (c) random coils. Now, certain criteria can be used to predict the occurrence of these structures in the secondary structure of the protein. This was first established by Chow and Fasman (1978) based on the propensity of certain amino acids associated with these structures, i.e., helix and beta sheet. For example, the amino acids glu, met, ala, and lys are predominantly associated with the helix structure whereas the amino acids val, ile, and tyr are strongly associated with the beta sheet structure. The amino acid leucine is associated with both the helix and the beta sheet. The amino acids glycine and proline occur as breakers of the helix proline usually occurs as the first residue in the helix. Also, asp and glu occurs at the N-terminus, whereas arg and lys occur at the C-terminus. 

Figure 8.40 Drawing of Raster 3D images for the dimer of the asymmetric unit glutathione S-transferase 3-3 from rat liver and B strands are indicated by yellow arrows and a helices by blue barrels. Active site tyrosine is shown in red and GSH in purple. The spatial relationship between the two active sites in the dimer is shown. (Modified from Xinhua Ji, Pinghu Zhang, Richard Armstrong and Gary Gilliland Biochemistry 31 10169-10184, 1992.)...

The structural studies on amicyanin from P. versutus show that the protein consists of nine B-strands that form into two antiparallel /3-sheets, giving the molecule an overall structural motif known as a /3-sandwich (see Fig. 4). This overall topology is very similar to that of other structurally characterized cupredoxins, with the homology to plastocyanin being greatest (87). The only notable difference between amicyanin and most other cupredoxin structures is the presence of a 21-residue N-tereminal extension that forms an extra /8-strand in the structure. The recently published structural studies (95, 96) on the type 1 blue copper protein rusticyanin show that it, too, possesses an... 

Figure 10 The crystal structure of P450cam with bound camphor. The secondary structure elements are shown schematically with cylinders representing a helices and ribbon arrows depicting B strands...

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