Herbert Waldmann

Publications (3)7.44 Total impact

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  Available from: Carsten Kötting

  Dataset: Supplemental Information

  Jörn Güldenhaupt, Till Rudack, Peter Bachler, Daniel Mann, Gemma Triola, Herbert Waldmann, Carsten Kötting, Klaus Gerwert
• Source

  Available from: Carsten Kötting

  Article: N-Ras Forms Dimers at POPC Membranes.

  Jörn Güldenhaupt, Till Rudack, Peter Bachler, Daniel Mann, Gemma Triola, Herbert Waldmann, Carsten Kötting, Klaus Gerwert
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  ABSTRACT: Ras is a central regulator of cellular signaling pathways. It is mutated in 20-30% of human tumors. To perform its function, Ras has to be bound to a membrane by a posttranslationally attached lipid anchor. Surprisingly, we identified here dimerization of membrane anchored Ras by combining attenuated total reflectance Fourier transform infrared spectroscopy, biomolecular simulations, and Förster resonance energy transfer experiments. By analyzing x-ray structural models and molecular-dynamics simulations, we propose a dimerization interface between α-helices 4 and 5 and the loop between β2 and β3. This seems to explain why the residues D47, E49, R135, R161, and R164 of this interface are influencing Ras signaling in cellular physiological experiments, although they are not positioned in the catalytic site. Dimerization could catalyze nanoclustering, which is well accepted for membrane-bound Ras. The interface could provide a new target for a seemingly novel type of small molecule interfering with signal transduction in oncogenic Ras mutants.
  Biophysical Journal 10/2012; 103(7):1585-93. · 3.65 Impact Factor
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  Available from: Carsten Kötting

  Article: Secondary structure of lipidated Ras bound to a lipid bilayer.

  Jörn Güldenhaupt, Yekbun Adigüzel, Jürgen Kuhlmann, Herbert Waldmann, Carsten Kötting, Klaus Gerwert
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  ABSTRACT: Ras proteins are small guanine nucleotide binding proteins that regulate many cellular processes, including growth control. They undergo distinct post-translational lipid modifications that are required for appropriate targeting to membranes. This, in turn, is critical for Ras biological function. However, most in vitro studies have been conducted on nonlipidated truncated forms of Ras proteins. Here, for the first time, attenuated total reflectance-FTIR studies of lipid-modified membrane-bound N-Ras are performed, and compared with nonlipidated truncated Ras in solution. For these studies, lipidated N-Ras was prepared by linking a farnesylated and hexadecylated N-Ras lipopeptide to a truncated N-Ras protein (residues 1-181). It was then bound to a 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine bilayer tethered on an attenuated total reflectance crystal. The structurally sensitive amide I absorbance band in the IR was detected and analysed to determine the secondary structure of the protein. The NMR three-dimensional structure of truncated Ras was used to calibrate the contributions of the different secondary structural elements to the amide I absorbance band of truncated Ras. Using this novel approach, the correct decomposition was selected from several possible solutions. The same parameter set was then used for the membrane-bound lipidated Ras, and provided a reliable decomposition for the membrane-bound form in comparison with truncated Ras. This comparison indicates that the secondary structure of membrane-bound Ras is similar to that determined for the nonlipidated truncated Ras protein for the highly conserved G-domain. This result validates the multitude of investigations of truncated Ras without anchor in vitro. The novel attenuated total reflectance approach opens the way for detailed studies of the interaction network of the membrane-bound Ras protein.
  FEBS Journal 01/2009; 275(23):5910-8. · 3.79 Impact Factor