FIGURE 3.

Regulatory function of IQ1 cannot be substituted by IQ3 or IQ5. A, consensus sequence of IQ1 motif of 12 mammalian myosin 5, including myosin 5a, 5b, 5c from mouse (GenBank^TM ID: Q99104, NM_201600, XM_198225), rat (GenBank^TM ID: Q9QYF3, P70569, EDL77808), cattle (GenBank^TM ID XP_002691008, XP_002691008, XP_002691009), and human (GenBank^TM ID: Q9Y4I1, Q9ULV0, Q9NQX4). X is any amino acid, B is a basic residue, φ is a hydrophobic residue, ψ is an aromatic residue, and ω is a small hydrophilic residue. B, sequence alignment of mouse myosin 5a IQ1, IQ3, and IQ5. C, ribbon drawing of apo-CaM (N-lobe, marine; C-lobe, magenta) in complex with IQ1 of muring myosin 5a (PDB # 2IX7). Orange residues, typical IQ motif residues IQXXXRGXXXR; green residues, conserved IQ1residues identified in this report (K765, L766, R767, W780, L781, and Y786). D and E, effects of GST-GTD on the actin-activated ATPase activity of MD-IQ3 (D) and MD-IQ5 (E) in EGTA (open triangles) or pCa4 conditions (closed triangles). MD-IQ3 and MD-IQ5 were created by substitution of IQ1 in MD-IQ1 with IQ3 and IQ5, respectively. Values are the average of two independent assays.