Binding Specificity of Avian Heat Shock Protein 108

• Published in: Biochemical and biophysical research communications Vol. 240; no. 3; pp. 673 - 676
• Main Authors: Weiner, Karen X.B., Hayes, Gary R., Lucas, John J.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 26.11.1997
• Subjects: Animals; Avidin - metabolism; Binding, Competitive; Carrier Proteins - metabolism; Cell Membrane - metabolism; CHICKENS; Conalbumin - analogs & derivatives; Conalbumin - metabolism; Ferric Compounds - metabolism; HSP70 Heat-Shock Proteins - metabolism; Iodine Radioisotopes - metabolism; Iron-Binding Proteins; Liver - metabolism; Membrane Proteins - metabolism; Ovalbumin - metabolism; Peptide Fragments - metabolism; POLLO; POULET; Protein Binding; Protein Denaturation; Transferrin-Binding Proteins; Trypsin - metabolism
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1006/bbrc.1997.7593

Chicken heat shock protein 108 (HSP108), the avian homolog of GRP94, was originally isolated from hen oviduct and binds Fe-ovotransferrin (Fe-OTf). The liver is also a rich source, and liver membranes bind Fe-OTf with a KDof 1.7 × 10−7M, a value similar to oviduct membranes. A competition assay, based on the binding of125I-Fe-OTf to liver membranes, was utilized to examine the binding specificity of HSP108. Ovalbumin and avidin competed effectively, with KD's of 1.8 × 10−7M and 1.4 × 10−7M, respectively. Iron-free OTf bound with a 10-fold higher KD. Egg white lysozyme, chicken IgG, human transferrin, rabbit muscle actin, and porcine insulin do not bind. Neither do denatured ovalbumin or ovalbumin tryptic peptides. Thus, the binding activity of HSP108 is not restricted to Fe-OTf, nor is it universal.