Integrin alpha5beta1 ligands: biological evaluation and conformational analysis.
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Biomedical subjects
Publications and source records attributed to Katherina Sewald.
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Using an RT-PCR approach a cDNA clone, designated Ms-Rac4 and putatively coding for a small GTPase was isolated from Medicago sativa. Ms-Rac4 and the earlier described Ms-Rac1 [Mol. Gen. Genet. 263 (2000) 761] belong to the class of GTP-binding Rho of plants (Rop) proteins. At the amino acid level they display all conserved regions that are common to GTP-binding proteins. Phylogenetically both are located in the group Ia, but within this group they are well-separated. Computed structure models of both proteins revealed a high degree of structural conservation. Particularly the switch I and switch II region are 100% conserved between Ms-Rac1 and Ms-Rac4 and highly conserved as compared to other Rac-like G-proteins. Both GTPases differ in structure within the fourth loop and the fourth helix. GTP-binding properties of the heterologously expressed Ms-Rac1 and Ms-Rac4 was shown by fluorescence resonance energy transfer (FRET) using mantGTP and by surface plasmon resonance (SPR). By this method the specificity of the G-protein/GTP interaction was shown and the inhibitory effect of GTP, EDTA and Mg(2+) on the Ms-Rac1 and Ms-Rac4 binding to immobilized GTP was characterized. Ms-Rac1 and Ms-Rac4 exhibited the same affinity to GTP and are similarly affected by GTP, EDTA and Mg(2+). Thus, the predicted structural differences do not result in different GTP-binding properties of Ms-Rac1 and Ms-Rac4.
Immobilized small-molecule inhibitors are suited for enrichment of biomolecules by affinity chromatography, as it is shown for metalloproteinases and an immobilizable derivative of the hydroxamate-type inhibitor marimastat. A new asymmetric synthesis of marimastat is presented that allows for site-specific attachment to a solid surface, e.g., a chromatography matrix or a surface plasmon resonance sensor chip. The latter technique is shown to be a valuable tool for the optimization of binding and elution conditons of biomolecules in affinity chromatography.