TY  - JOUR
A1  - Schuler, Benjamin
A1  - Fürst, Frank
A1  - Osterroth, Frank
A1  - Steinbacher, Stefan
A1  - Huber, Robert
A1  - Seckler, Robert
T1  - Plasticity and steric strain in a parallel beta-helix: Rational mutations in P22 tailspike protein
N2  - By means of genetic screens, a great number of mutations that affect the folding and stability of the tailspike protein from Salmonella phage P22 have been identified. Temperature-sensitive folding (tsf) mutations decrease folding yields at high temperature, but hardly affect thermal stability of the native trimeric structure when assembled at low temperature. Global suppressor (su) mutations mitigate this phenotype. Virtually all of these mutations are located in the central domain of tailspike, a large parallel beta-helix. We modified tailspike by rational single amino acid replacements at three sites in order to investigate the influence of mutations of two types: (1) mutations expected to cause a tsf phenotype by increasing the side-chain volume of a core residue, and (2) mutations in a similar structural context as two of the four known su mutations, which have been suggested to stabilize folding intermediates and the native structure by the release of backbone strain, an effect well known for residues that are primarily evolved for function and not for stability or folding of the protein. Analysis of folding yields, refolding kinetics and thermal denaturation kinetics in vitro show that the tsf phenotype can indeed be produced rationally by increasing the volume of side chains in the beta-helix core. The high-resolution crystal structure of mutant T326F proves that structural rearrangements only take place in the remarkably plastic lumen of the beta-helix, leaving the arrangement of the hydrogen-bonded backbone and thus the surface of the protein unaffected. This supports the notion that changes in the stability of an intermediate, in which the beta-helix domain is largely formed, are the essential mechanism by which tsf mutations affect tailspike folding. A rational design of su mutants, on the other hand, appears to be more difficult. The exchange of two residues in the active site expected to lead to a drastic release of steric strain neither enhanced the folding properties nor the stability of tailspike. Apparently, side-chain interactions in these cases overcompensate for backbone strain, illustrating the extreme optimization of the tailspike protein for conformational stability. The result exemplifies the view arising from the statistical analysis of the distribution of backbone dihedral angles in known three-dimensional protein structures that the adoption of straight phi/psi angles other than the most favorable ones is often caused by side-chain interactions.
Y1  - 2000
UR  - http://www3.interscience.wiley.com/cgi-bin/abstract/71001984/START
ER  - 
TY  - JOUR
A1  - Pattyn, Frank
A1  - Perichon, Laura
A1  - Durand, Gael
A1  - Favier, Lionel
A1  - Gagliardini, Olivier
A1  - Hindmarsh, Richard C. A.
A1  - Zwinger, Thomas
A1  - Albrecht, Torsten
A1  - Cornford, Stephen
A1  - Docquier, David
A1  - Furst, Johannes J.
A1  - Goldberg, Daniel
A1  - Gudmundsson, Gudmundur Hilmar
A1  - Humbert, Angelika
A1  - Huetten, Moritz
A1  - Huybrechts, Philippe
A1  - Jouvet, Guillaume
A1  - Kleiner, Thomas
A1  - Larour, Eric
A1  - Martin, Daniel
A1  - Morlighem, Mathieu
A1  - Payne, Anthony J.
A1  - Pollard, David
A1  - Rueckamp, Martin
A1  - Rybak, Oleg
A1  - Seroussi, Helene
A1  - Thoma, Malte
A1  - Wilkens, Nina
T1  - Grounding-line migration in plan-view marine ice-sheet models: results of the ice2sea MISMIP3d intercomparison
JF  - Journal of glaciology
N2  - Predictions of marine ice-sheet behaviour require models able to simulate grounding-line migration. We present results of an intercomparison experiment for plan-view marine ice-sheet models. Verification is effected by comparison with approximate analytical solutions for flux across the grounding line using simplified geometrical configurations (no lateral variations, no buttressing effects from lateral drag). Perturbation experiments specifying spatial variation in basal sliding parameters permitted the evolution of curved grounding lines, generating buttressing effects. The experiments showed regions of compression and extensional flow across the grounding line, thereby invalidating the boundary layer theory. Steady-state grounding-line positions were found to be dependent on the level of physical model approximation. Resolving grounding lines requires inclusion of membrane stresses, a sufficiently small grid size (<500 m), or subgrid interpolation of the grounding line. The latter still requires nominal grid sizes of <5 km. For larger grid spacings, appropriate parameterizations for ice flux may be imposed at the grounding line, but the short-time transient behaviour is then incorrect and different from models that do not incorporate grounding-line parameterizations. The numerical error associated with predicting grounding-line motion can be reduced significantly below the errors associated with parameter ignorance and uncertainties in future scenarios.
Y1  - 2013
U6  - https://doi.org/10.3189/2013JoG12J129
SN  - 0022-1430
VL  - 59
IS  - 215
SP  - 410
EP  - 422
PB  - International Glaciological Society
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - VanDerLoop, Frank T. L.
A1  - VanDerVen, Peter F. M
A1  - Fürst, Dieter Oswald
A1  - Gautel, Mathias
A1  - VanEys, Guillaume
A1  - Ramaekers, Frans C. S.
T1  - Integration of titin into the sarcomeres of cultured differentiating human skeletal muscle cells
Y1  - 1996
ER  -