The actin-binding protein filamin links membrane receptors to the underlying cytoskeleton. The cytoplasmic domains of these membrane receptors have been shown to bind to various filamin immunoglobulin repeats. Notably, among 24 human filamin repeats, repeat 17 was reported to specifically bind to platelet receptor glycoprotein Ib␣ and repeat 21 to integrins. However, a complete sequence alignment of all 24 human filamin repeats reveals that repeats 17 and 21 actually belong to a distinct filamin repeat subgroup (containing repeats 4, 9, 12, 17, 19, 21, and 23) that shares a conserved ligand-binding site. Using isothermal calorimetry and NMR analyses, we show that all repeats in this subgroup can actually bind glycoprotein Ib␣, integrins, and a cytoskeleton regulator migfilin in similar manners. These data provide a new view on the ligand specificity of the filamin repeats. They also suggest a multiple ligand binding mechanism where similar repeats within a filamin monomer may promote receptor clustering or receptor cross-talking for regulation of the cytoskeleton organization and diverse filaminmediated cellular activities.

Because of clerical errors in preparing the figures, in Fig. 1A, the last portions of the mouse and human TILRR sequences are not aligned with the consensus sequence, and the human form is mislabeled as 716 amino acids (aa). In Fig. 2C (and on page 7227, right column, line 4), the most potent form of the human protein is mislabeled as 710 aa. Supplemental Fig. S1 correctly shows the alignment and the length of the human TILRR protein as 715 aa, with the most potent form, lacking the N-terminal 6 aa, as 709 aa. The amino acid sequence is correct as shown in all figures, and the clerical errors have no impact on any of the results, including the function of the protein, the probes used, or the numbering of the mutants.

Gas-liquid chromatography was used to measure low pressure solubilities of nine volatile solutes in polyethylene and in copolymers of ethylene and vinyl acetate containing 3.95, 9.2, and 30.3 wt % vinyl acetate. Solubilities in ethylene-free poly(vinyl acetate) were reported earlier. The solutes studied are methyl ethyl ketone, acetone, isopropyl alcohol, vinyl acetate, sulfur dioxide, methyl chloride, ethane, ethylene, and carbon dioxide. While gas-liquid chromatography provides a rapid and simple method for measuring solubilities, experimental precautions must be observed to assure reliable results. Such precautions are particularly important for sparingly soluble solutes (e.g., ethane, ethylene, carbon dioxide) where the measured solubilities tend to be less accurate than those attained with higher-boiling solvents.

No abstract