THE MEMBRANE FORM OF ACETYLCHOLINESTERASE FROM RAT-BRAIN CONTAINS A 20 KDA HYDROPHOBIC ANCHOR

Rat brain acetylcholinesterase (AChE, EC 3.1.1.7) consists of about 80% amphiphilic detergent-soluble (DS-) AChE and 20% hydrophilic salt-soluble (SS-) AChE. DS-AChE contains about 65% tetrameric, 20% dimeric and 10% monomeric, SS-AChE about 40% tetrameric and 60% monomeric forms. N-terminal sequencing of DS- and SS-AChE gave identical N-termini corresponding to the published cDNA sequence of the mature enzyme. The band pattern on SDS-gels is similar to that of AChE from human and bovine brain. SDS-PAGE of hydrophobically labeled DS-AChE revealed the presence of a disulfide bonded hydrophobic membrane anchor of about 20 kDa. Monoclonal antibodies (mAbs) recognizing the anchor-containing subunits of mammalian brain DS-AChE, crossreacted with rat brain DS-AChE but not with SS-AChE. DS- and SS-AChE also reacted with antibodies raised against a peptide comprising the last 10 amino acids of the sequence of bovine brain AChE. Our results led us to conclude that both DS- and SS-AChE from rat brain contain T-type catalytic subunits, and DS-AChE in addition a P-type hydrophobic anchor similar to other mammalian brain DS-AChE.