Binding specificity of avian heat shock protein 108.
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 KD of 1.7 x 10(-7) M, a value similar to oviduct membranes. A competition assay, based on the binding of 125I-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 x 10(-7) M and 1.4 x 10(-7) M, 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.
Weiner
K X
KX
Department of Biochemistry and Molecular Biology, SUNY Health Science Center, Syracuse 13210, USA.
Hayes
G R
GR
Lucas
J J
JJ
D000818:Animals; D001360:Avidin / Q000378:metabolism; D001667:Binding, Competitive; D002352:Carrier Proteins / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D002645:Chickens; D003207:Conalbumin / Q000031:analogs & derivatives* / Q000378:metabolism; D005290:Ferric Compounds / Q000378:metabolism*; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D007457:Iodine Radioisotopes / Q000378:metabolism; D033862:Iron-Binding Proteins; D008099:Liver / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D010047:Ovalbumin / Q000378:metabolism; D010446:Peptide Fragments / Q000378:metabolism; D011485:Protein Binding; D011489:Protein Denaturation; D033863:Transferrin-Binding Proteins; D014357:Trypsin / Q000378:metabolism
D002352:Carrier Proteins; D005290:Ferric Compounds; D018840:HSP70 Heat-Shock Proteins; D007457:Iodine Radioisotopes; D033862:Iron-Binding Proteins; D008565:Membrane Proteins; D010446:Peptide Fragments; D033863:Transferrin-Binding Proteins; C057592:diferric ovotransferrin; C018551:glucose-regulated proteins; D003207:Conalbumin; D001360:Avidin; D010047:Ovalbumin; D014357:Trypsin