Molecular characteristics of the novel intermediate filament protein paranemin. Sequence reveals EAP-300 and IFAPa-400 are highly homologous to paranemin.
Paranemin was initially found to copurify with the intermediate filament (IF) proteins vimentin and desmin from embryonic chick skeletal muscle and was described as an IF-associated protein (IFAP). We have purified paranemin from embryonic chick skeletal muscle, prepared antibodies, and demonstrated that they label at the Z-lines of both adult avian and porcine cardiac and skeletal muscle myofibrils. We determined the cDNA sequence of paranemin by immunoscreening a lambdagt22A cDNA library from embryonic chick skeletal muscle. Northern blot analysis revealed a single transcript of 5.3 kilobases, which is much smaller than predicted from the size of paranemin (280 kDa) by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The derived amino acid sequence of paranemin (1,606 residues; 178,161 kDa) contains the conserved IF rod domain (308 amino acids), which has highest homology to the rod domains of nestin and tanabin. Thus, paranemin is an IF protein rather than an IFAP. Sequence analysis also revealed that the partial cDNA sequences of two proteins, namely EAP-300 and IFAPa-400, are almost identical to regions of the cDNA sequence of paranemin. The complete paranemin cDNA was expressed in a cell line (SW13) with, and without, detectable cytoplasmic IFs. Antibody labeling of these cells suggests that paranemin does not form IFs by itself, but rather is incorporated into heteropolymeric IFs with vimentin.
Hemken
P M
PM
Muscle Biology Group, Departments of Biochemistry and Biophysics and of Animal Science, Iowa State University, Ames, Iowa 50011-3260, USA.
Bellin
R M
RM
Sernett
S W
SW
Becker
B
B
Huiatt
T W
TW
Robson
R M
RM
D000595:Amino Acid Sequence; D000818:Animals; D030161:Avian Proteins; D001483:Base Sequence; D015152:Blotting, Northern; D002642:Chick Embryo; D002848:Chromatography, DEAE-Cellulose; D002850:Chromatography, Gel; D003001:Cloning, Molecular; D018076:DNA, Complementary; D004591:Electrophoresis, Polyacrylamide Gel; D005904:Glial Fibrillary Acidic Protein / Q000235:genetics*; D007381:Intermediate Filament Proteins; D008969:Molecular Sequence Data; D009124:Muscle Proteins / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D018482:Muscle, Skeletal / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000235:genetics*; D064231:Nestin; D017386:Sequence Homology, Amino Acid; D014162:Transfection
D030161:Avian Proteins; D018076:DNA, Complementary; D005904:Glial Fibrillary Acidic Protein; D007381:Intermediate Filament Proteins; D009124:Muscle Proteins; D009419:Nerve Tissue Proteins; D064231:Nestin; C034429:paranemin protein, chicken