Human lymphocyte-specific protein 1, the protein overexpressed in neutrophil actin dysfunction with 47-kDa and 89-kDa protein abnormalities (NAD 47/89), has multiple F-actin binding domains.
Human lymphocyte-specific protein 1 (LSP1) is an F-actin binding protein, which has an acidic N-terminal half and a basic C-terminal half. In the basic C-terminal half, there are amino acid sequences highly homologous to the actin-binding domains of two known F-actin binding proteins: caldesmon and the villin headpieces (CI, CII, VI, VII). However, the exact numbers and locations of the F-actin binding domains within LSP1 are not clearly defined. In this report, we utilized 125I-labeled F-actin ligand blotting and high-speed F-actin cosedimentation assays to analyze the F-actin binding properties of truncated LSP1 peptides and to define the F-actin binding domains. Results show that LSP1 has at least three and potentially a fourth F-actin binding domain. All F-actin binding domains are located in the basic C-terminal half and correspond to the caldesmon and villin headpiece homologous regions. LSP1 181-245 and LSP1 246-295, containing sequences homologous to caldesmon F-actin binding site I and II, respectively (CI, CII), binds F-actin; similarly, LSP1 306-339 can bind F-actin and contains two inseparable villin headpiece-like F-actin binding domains (VI, VII). Although LSP1 1-305, which does not contain VI and VII regions, retains F-actin binding activity, its binding affinity for F-actin is much weaker than that of full-length LSP1. Site-directed mutagenesis of the basic amino acids in the KRYK (VI) or KYEK (VII) sequences to acidic amino acids create mutants that bind F-actin with lower affinity than full-length wild-type LSP1. High KCl concentrations decrease full-length LSP1 binding to F-actin, suggesting the affinity between LSP1 and F-actin is mainly through electrostatic interaction.
Department of Cell Biology, School of Medicine, University of Alabama, Birmingham, AL 35295, USA.
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D000199:Actins / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D002135:Calcium-Binding Proteins / Q000096:biosynthesis* / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D002148:Calmodulin-Binding Proteins / Q000737:chemistry / Q000378:metabolism; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008840:Microfilament Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D016297:Mutagenesis, Site-Directed; D009504:Neutrophils / Q000378:metabolism* / Q000473:pathology*; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding / Q000235:genetics; D017434:Protein Structure, Tertiary / Q000235:genetics; D011817:Rabbits; D017386:Sequence Homology, Amino Acid; D055672:Static Electricity
D000199:Actins; D002135:Calcium-Binding Proteins; D002148:Calmodulin-Binding Proteins; D002352:Carrier Proteins; C034037:F-actin-binding proteins; C489183:LSP1 protein, human; D008840:Microfilament Proteins; D010446:Peptide Fragments; C026615:villin