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Background: Designing amino acid sequences that are stable in a given target structure amounts to maximizing a conditional probability. A straightforward approach to accomplishing this is a nested Monte Carlo where the conformation space is explored over and over again for different fixed sequences; this requires excessive computational demand. Several approximate attempts to remedy this situation,...
Background: The recent merger of computation and protein design has resulted in a burst of success in the generation of novel proteins with native-like properties. A critical component of this coupling between theory and experiment is a detailed analysis of the structures and stabilities of designed proteins to assess and improve the accuracy of design algorithms.Results: Here we report the solution...
Background: Several deterministic and stochastic combinatorial optimization algorithms have been applied to computational protein design and homology modeling. As structural targets increase in size, however, it has become necessary to find more powerful methods to address the increased combinatorial complexity.Results: We present a new deterministic combinatorial search algorithm called 'Branch-and-Terminate'...
Background: Both backbone hydrogen bonding and interactions between sidechains stabilize β sheets. Cross-strand interactions are the closest contacts between the sidechains of a β sheet. Here we investigate the energetics of cross-strand interactions using a variant of the B1 domain of immunoglobulin G (IgG) binding protein G (β1) as our model system.Results: Pairwise mutations of polar and nonpolar...
Background: The parallel two-stranded α-helical coiled coil is the most frequently encountered subunit-oligomerization motif in proteins. The simplicity and regularity of this motif have made it an attractive system to explore some of the fundamental principles of protein folding and stability and to test the principles of de novo design.Results: The X-ray crystal structure of the 18-heptad-repeat...
Many different zinc binding modules have been identified. Their abundance and variety suggests that the formation of zinc binding folds might be relatively common. We have determined the structure of CH1 1 , a 27-residue peptide derived from the first cysteine/histidine-rich region (CH1) of CREB binding protein (CBP). This peptide forms a highly ordered zinc-dependent fold that is distinct...
To investigate how electrostatic interactions restrict the associations of coiled coils, we improved a heterodimeric coiled coil (WinZip-A1B1) by in vivo selection and, alternatively, by rational design. Selection from libraries encoding variable edge (g and e) residues enriched g/e' ion pairs, but the optimum selected heterodimers unexpectedly retained two predicted repulsive g/e' pairs. The best...
In a designed fusion protein the trimeric domain foldon from bacteriophage T4 fibritin was connected to the C terminus of the collagen model peptide (GlyProPro) 10 by a short Gly-Ser linker to facilitate formation of the three-stranded collagen triple helix. Crystal structure analysis at 2.6 A resolution revealed conformational changes within the interface of both domains compared with...
The tetratricopeptide repeat (TPR) is a 34-amino acid α-helical motif that occurs in over 300 different proteins. In the different proteins, three to sixteen or more TPR motifs occur in tandem arrays and function to mediate protein-protein interactions. The binding specificity of each TPR protein is different, although the underlying structural motif is the same. Here we describe a statistical approach...
Conformational dynamics has an established role in enzyme catalysis, but its contribution to ligand binding and specificity is largely unexplored. Here we used the Tiam1 PDZ domain and an engineered variant (QM PDZ) with broadened specificity to investigate the role of structure and conformational dynamics in molecular recognition. Crystal structures of the QM PDZ domain both free and bound to ligands...
Although protein design has been used to introduce new functions, designed variants generally only function as well as natural proteins after rounds of laboratory evolution. One possibility for this pattern is that designed mutants frequently sample nonfunctional conformations. To test this idea, we exploited advances in multiconformer modeling of room-temperature X-ray data collection on redesigned...
Antibody fragments are frequently used as a “crystallization chaperone” to aid structural analysis of complex macromolecules that are otherwise crystallization resistant, but conventional fragment formats have not been designed for this particular application. By fusing an anti-parallel coiled-coil structure derived from the SARAH domain of human Mst1 kinase to the variable region of an antibody,...
Glaucoma-associated myocilin is a member of the olfactomedins, a protein family involved in neuronal development and human diseases. Molecular studies of the myocilin N-terminal coiled coil demonstrate a unique tripartite architecture: a Y-shaped parallel dimer-of-dimers with distinct tetramer and dimer regions. The structure of the dimeric C-terminal 7-heptad repeats elucidates an unexpected repeat...
Solvent molecules interact intimately with proteins and can profoundly regulate their structure and function. However, accurately and efficiently modeling protein solvation effects at the molecular level has been challenging. Here, we present a method that improves the atomic-level modeling of soluble and membrane protein structures and binding by efficiently predicting de novo protein-solvent molecule...
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