title: Specificity of binding of the plectin actin-binding domain to beta4 integrin.
abstract: Plectin is a major component of the cytoskeleton and links the intermediate filament system to hemidesmosomes by binding to the integrin beta4 subunit. Previously, a binding site for beta4 was mapped on the actin-binding domain (ABD) of plectin and binding of beta4 and F-actin to plectin was shown to be mutually exclusive. Here we show that only the ABDs of plectin and dystonin bind to beta4, whereas those of other actin-binding proteins do not. Mutations of the ABD of plectin-1C show that Q131, R138, and N149 are critical for tight binding of the ABD to beta4. These residues form a small cavity, occupied by a well-ordered water molecule in the crystal structure. The beta4 binding pocket partly overlaps with the actin-binding sequence 2 (ABS2), previously shown to be essential for actin binding. Therefore, steric interference may render binding of beta4 and F-actin to plectin mutually exclusive. Finally, we provide evidence indicating that the residues preceding the ABD in plectin-1A and -1C, although unable to mediate binding to beta4 themselves, modulate the binding activity of the ABD for beta4. These studies demonstrate the unique property of the plectin-ABD to bind to both F-actin and beta4, and explain why several other ABD-containing proteins that are expressed in basal keratinocytes are not recruited into hemidesmosomes.
mesh_terms: D000199:Actins / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D002352:Carrier Proteins; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D003598:Cytoskeletal Proteins / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism*; D000071821:Dystonin; D005455:Fluorescent Antibody Technique; D006801:Humans; D039663:Integrin beta4 / Q000378:metabolism*; D007381:Intermediate Filament Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000378:metabolism; D051190:Plectin; D011485:Protein Binding; D020033:Protein Isoforms / Q000235:genetics; D017434:Protein Structure, Tertiary; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016415:Sequence Alignment; D020798:Two-Hybrid System Techniques
chemical_list: D000199:Actins; D002352:Carrier Proteins; D003598:Cytoskeletal Proteins; C486268:DST protein, human; D000071821:Dystonin; D039663:Integrin beta4; D007381:Intermediate Filament Proteins; D009419:Nerve Tissue Proteins; C495332:PLEC protein, human; C495334:Plec protein, rat; D051190:Plectin; D020033:Protein Isoforms