Structural Basis of the Activity of the Microtubule‐Stabilizing Agent Epothilone A Studied by NMR Spectroscopy in Solution

The Tubulin Binding Mode of MT Stabilizing and Destabilizing Agents Studied by NMR

“…The latter change affects mainly the position of the 3-OH that, upon binding, experiences a 3.8 Å shift movement from the inside of the macrocycle to an exposed position in its exterior. The authors proposed that this change makes the 3-OH more accessible for H-bonding to tubulin side chains [96] , although more recent findings suggest that the 3-OH does not participate in direct contacts to tubulin but is rather exposed to the solvent (see next section) [76,95] . The importance of the geometry of this segment Fig.…”

“…Recently, the [96] ) and by electron crystallography from zinc-stabilized tubulin sheets ( bottom right [26] conformation of EpoA and two C3-modified analogues was also investigated in aqueous solution by means of NMR spectroscopy and NAMFIS calculations [95] ; results will be discussed later in this section. Two conformations of EpoA in complex with tubulin have been proposed on the basis of EC [26] and NMR [76,96] data, respectively ( Fig. 11 ).…”

“…In this case, the problem of the binding orientation of B can be reduced to determine the relative orientation of the two ligands A and B in the protein binding site. A new NMR-based method (INPHARMA) was developed to address this question and applied to the binding of EpoA and tubulin [75,76] .…”

Evaluation of Solvent Accessibility Epitopes for Different Dehydrogenase Inhibitors

“…Most of these methods are based on the transfer of magnetization from the protein to the ligand [2][3][4] or between ligands. [5][6][7] WaterLOGSY has been employed for drug screening because it is one of the most sensitive NMR techniques used in the context of drug design although it has until recently not been used to map the ligand binding epitope. However, recent experiments show that a solvent accessibility epitope can be derived from such experiments which can be translated into the orientation of a ligand with respect to the protein or can be used to compare solvent accessibility epitopes for different ligands.…”

Total Synthesis and Selective Activity of a New Class of Conformationally Restrained Epothilones

“…[9] The role of the N atom at an ortho-position in the heterocycle has been attributed to a hydrogen-bond interaction between the thiazole N atom and a protonated His residue in tubulin. [10][11][12][13] The 16-Me and 19-H adopt a syn orientation, liberating the thiazole N atom from the steric bulk of the 16-Me, making it more accessible for potential hydrogen bonding. Rigidification of the aromatic side chain through incorporation of the C-16-C-17 olefinic double bond into a fused heteroaromatic ring system such as benzothiazole resulted in analogues more potent than parent epothilone B and D. [14,15] Interestingly, in contrast to the pyridine analogues, there was no dependence of the tubulinpolymerizing activity of these rigidified analogues on the position of the nitrogen atom in the heterocycles.…”