Effect of protamine on the solubilization of collagen-tailed acetylcholinesterase: potential heparin-binding consensus sequences in the tail of the enzyme.
Asymmetric acetylcholinesterase (AChE) contains three tetrameric sets of catalytic subunits disulfide-linked to structural subunits of a collagenic tail. This form is localized in the basement membrane zone of the neuromuscular junction, where it interacts with proteoglycans. It has been described that heparin-binding domains of many proteins contains clusters of basic residues. Here we show that protamine--a highly basic protein--specifically solubilizes asymmetric AChE from the rat neuromuscular junction, starting at 25 micrograms/ml and reaching a plateau at 250 micrograms/ml protamine. We also show that protamine was able to displace AChE bound to heparin-agarose. Two synthetic peptides corresponding to the sequence of the collagenic tail polypeptide also release the enzyme. Finally, we propose that two heparin-binding consensus sequences (-B-B-X-B-) are present in the tail of AChE. Our results indicate that clusters of basic residues are responsible for the interaction of the collagen-tailed AChE with proteoglycans.
Deprez
P N
PN
Departamento de Biología Celular y Molecular Facultad de Ciencias Biológicas Pontificia Universidad Católica de Chile, Santiago.
Signorelli
J
J
Inestrosa
N C
NC
D000110:Acetylcholinesterase / Q000737:chemistry* / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D002846:Chromatography, Affinity; D003094:Collagen / Q000737:chemistry*; D016384:Consensus Sequence; D005260:Female; D006493:Heparin / Q000737:chemistry* / Q000378:metabolism; D008969:Molecular Sequence Data; D009469:Neuromuscular Junction / Q000201:enzymology; D010455:Peptides / Q000138:chemical synthesis / Q000737:chemistry; D011479:Protamines / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012995:Solubility
D010455:Peptides; D011479:Protamines; D006493:Heparin; D003094:Collagen; D000110:Acetylcholinesterase