Structures of three crystal forms of the sweet protein thaumatin

Abstract

Three crystal forms of the sweet-tasting protein thaumatin from the African berry Thaumatococcus daniellii have been grown. These include two naturally occurring isoforms, A and B, that differ by a single amino acid, and a recombinant form of isoform B expressed in yeast. The crystals are of space groups C2 with a = 117.7, b = 44.9, c = 38.0 A, and beta = 94.0 degrees, P2(1)2(1)2(1) with a = 44.3, b = 63.7 and c = 72.7 A, and a tetragonal form P4(1)2(1)2 with a = b = 58.6 and c = 151.8 A. The structures of all three crystals have been solved by molecular replacement and subsequently refined to R factors of 0.184 for the monoclinic at 2.6 A, 0.165 for the orthorhombic at 1.75 A, and 0.181 for the tetragonal, also at 1.75 A resolution. No solvent was included in the monoclinic crystal while 123 and 105 water molecules were included in the higher resolution orthorhombic and tetragonal structures, respectively. A bound tartrate molecule was also clearly visible in the tetragonal structure. The r.m.s. deviations between molecular structures in the three crystals range from 0.6 to 0.7 A for Calpha atoms, and 1.1 to 1.3 A for all atoms. This is comparable to the r.m.s. deviation between the three structures and the starting model. Nevertheless, several peptide loops show particularly large variations from the initial model.

Atomic Force Microscopy Investigation of Vaccinia Virus Structure

“…5) (14) might be consistent with such a model. The collapsibility of the core wall would be consistent with the presence of an apparent external bracing during virion assembly (provided by the vaccinia virus D13 protein's clathrin-like networks) (11,31). The core wall may be built within such a template, or mold, within the crescents that are characteristic of the early stages of virion morphogenesis.…”

His22 of TLXI plays a critical role in the inhibition of glycoside hydrolase family 11 xylanases

“…A molecular model of TLXI was generated with MOE (The Molecular Operating Environment) (Chemical Computing Group Inc., Montreal, Canada) using the structure of thaumatin (PDB code 1THV [23]) as template. The sequence-alignment provided by the genthreader threading algorithm [24] was adapted in order to obtain a better model.…”

Phasing at high resolution using Ta6Br12cluster

“…The four test proteins, glucose isomerase (Carrell et al, 1989), thaumatin (Ko et al, 1994), thermolysin (Holmes & Matthews, 1982) and lysozyme (McPherson, 1982), were crystallized as described previously. The crystallization conditions for the four proteins are summarized in Table 1.…”