Axel J. Scheidig

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The 2.0 A crystal structure of the N6-adenine DNA methyltransferase M.TaqI in complex with specific DNA and a nonreactive cofactor analog reveals a previously unrecognized stabilization of the extrahelical target base. To catalyze the transfer of the methyl group from the cofactor S-adenosyl-l-methionine to the 6-amino group of adenine within the(More)
Microbial rhodopsins, which constitute a family of seven-helix membrane proteins with retinal as a prosthetic group, are distributed throughout the Bacteria, Archaea and Eukaryota. This family of photoactive proteins uses a common structural design for two distinct functions: light-driven ion transport and phototaxis. The sensors activate a signal(More)
The activities of three Rab-specific factors with GDP/GTP exchange activity, Vps9p, Rabex-5 and DSS4, with their cognate GTPases, Ypt51p, Rab5 and Ypt1p, have been analysed quantitatively. In contrast to other exchange factors examined and to DSS4, Vps9p, and by analogy probably Rabex-5, have considerably lower affinity than GDP to the respective GTPases.(More)
BACKGROUND In numerous biological events the hydrolysis of guanine triphosphate (GTP) is a trigger to switch from the active to the inactive protein form. In spite of the availability of several high-resolution crystal structures, the details of the mechanism of nucleotide hydrolysis by GTPases are still unclear. This is partly because the structures of the(More)
A photosystem II preparation from the thermophilic cyanobacterium Synechococcus elongatus, which is especially suitable for three-dimensional crystallization in a fully active form was developed. The efficient purification method applied here yielded 10 mg of protein of a homogenous dimeric complex of about 500 kDa within 2 days. Detailed characterization(More)
We present the 1.9 A resolution crystal structure of the catalytic domain of Gyp1p, a specific GTPase activating protein (GAP) for Ypt proteins, the yeast homologues of Rab proteins, which are involved in vesicular transport. Gyp1p is a member of a large family of eukaryotic proteins with shared sequence motifs. Previously, no structural information was(More)
The crystal structures of the inhibitor domain of Alzheimer's amyloid beta-protein precursor (APPI) complexed to bovine chymotrypsin (C-APPI) and trypsin (T-APPI) and basic pancreatic trypsin inhibitor (BPTI) bound to chymotrypsin (C-BPTI) have been solved and analyzed at 2.1 A, 1.8 A, and 2.6 A resolution, respectively. APPI and BPTI belong to the Kunitz(More)
FTIR difference spectroscopy has been established as a new tool to study the GTPase reaction of H-ras p21 (Ras) in a time-resolved mode at atomic resolution without crystallization. The phosphate vibrations were analyzed using site specifically 18O-labeled caged GTP isotopomers. One nonbridging oxygen per nucleotide was replaced for an 18O isotope in the(More)
The sulfur cycle enzyme sulfane dehydrogenase SoxCD is an essential component of the sulfur oxidation (Sox) enzyme system of Paracoccus pantotrophus. SoxCD catalyzes a six-electron oxidation reaction within the Sox cycle. SoxCD is an α(2)β(2) heterotetrameric complex of the molybdenum cofactor-containing SoxC protein and the diheme c-type cytochrome SoxD(More)
Geranylgeranylation is a post-translational modification of Rab GTPases that enables them to associate reversibly with intracellular membranes. Geranylgeranylation of Rab proteins is critical for their activity in controlling intracellular membrane transport. According to the currently accepted model for their action, newly synthesized Rab proteins are(More)