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We characterized in detail the actin binding site of the small actin‐sequestering protein thymosin beta 4 (T beta 4) using chemically synthesized full‐length T beta 4 variants. The N‐terminal part (residues 1–16) and a hexapeptide motif (residues 17–22) form separate structural entities. In both, we identified charged and hydrophobic residues that participate in the actin interaction using chemical cross‐linking, complex formation in native gels and actin‐sequestering experiments. Quantitative data on the activity of the variants and circular dichroism experiments allow to present a model in which the N‐terminal part needs to adopt an alpha‐helix for actin binding and interacts through a patch of hydrophobic residues (6M‐I‐F12) on one side of this helix. Also, electrostatic contacts between actin and lysine residues 18, in the motif, and 14, in the N‐terminal alpha‐helix, appear important for binding. The residues critical for contacting actin are conserved throughout the beta‐thymosin family and in addition to this we identify a similar pattern in the C‐terminal headpiece of villin and dematin.

Cell migration is central to the development and maintenance of multicellular organisms. Fundamental understanding of cell migration can, for example, direct novel therapeutic strategies to control invasive tumor cells. However, the study of cell migration yields an overabundance of experimental data that require demanding processing and analysis for results extraction. Computational methods and tools have therefore become essential in the quantification and modeling of cell migration data. We review computational approaches for the key tasks in the quantification of in vitro cell migration: image pre-processing, motion estimation and feature extraction. Moreover, we summarize the current state-of-the-art for in silico modeling of cell migration. Finally, we provide a list of available software tools for cell migration to assist researchers in choosing the most appropriate solution for their needs.