TY - JOUR
T1 - Human erythrocyte acetylcholinesterase is an amphipathic protein whose short membrane-binding domain is removed by papain digestion
AU - Dutta-Choudhury, T. A.
AU - Rosenberry, T. L.
N1 - Copyright:
Copyright 2004 Elsevier B.V., All rights reserved.
PY - 1984
Y1 - 1984
N2 - Human erythrocyte acetylcholinesterase was shown to be an amphipathic protein in which proteases could cleave the hydrophobic domain from the enzymatically active hydrophilic domain. Papain and Pronase cleaved these domains with greatest efficiency, as measured by the disaggregation of purified acetylcholinesterase to disulfide-linked dimers (G2) on sucrose density gradients in the absence of detergent. Nonspecific proteolytic degradation was reduced both by the inclusion of edrophonium chloride, which protected acetylcholinesterase from inactivation, and by covalent attachment of papain to Sepharose CL-4B. In contrast to nondigested control acetylcholinesterase, the papain-disaggregated enzyme did not bind detergent according to hydrodynamic criteria and could not be reconstituted into liposomes. Thus, we conclude that the hydrophobic domain removed by papain digestion is in fact the membrane-binding domain in situ. This domain appeared largely inaccessible to proteases in intact erythrocytes, however, as less than 10% of the enzyme activity was solubilized by protease digestion. The hydrophobic domain removed by papain appeared very small, as nondigested control and disaggregated enzyme were identical in molecular weight and amino acid composition within experimental error. The fully reduced 75-kDa catalytic subunits of nondigested control enzyme appeared about 2 kDa larger than the corresponding subunits of disaggregated enzyme on polyacrylamide gel electrophoresis in sodium dodecyl sulfate, an indication that the hydrophobic domain was cleaved from the COOH or NH2 terminus of the catalytic subunit primary structure. Studies in which the NH-terminal amino acid was labeled by reductive methylation suggested that the hydrophobic domain is at the COOH terminus.
AB - Human erythrocyte acetylcholinesterase was shown to be an amphipathic protein in which proteases could cleave the hydrophobic domain from the enzymatically active hydrophilic domain. Papain and Pronase cleaved these domains with greatest efficiency, as measured by the disaggregation of purified acetylcholinesterase to disulfide-linked dimers (G2) on sucrose density gradients in the absence of detergent. Nonspecific proteolytic degradation was reduced both by the inclusion of edrophonium chloride, which protected acetylcholinesterase from inactivation, and by covalent attachment of papain to Sepharose CL-4B. In contrast to nondigested control acetylcholinesterase, the papain-disaggregated enzyme did not bind detergent according to hydrodynamic criteria and could not be reconstituted into liposomes. Thus, we conclude that the hydrophobic domain removed by papain digestion is in fact the membrane-binding domain in situ. This domain appeared largely inaccessible to proteases in intact erythrocytes, however, as less than 10% of the enzyme activity was solubilized by protease digestion. The hydrophobic domain removed by papain appeared very small, as nondigested control and disaggregated enzyme were identical in molecular weight and amino acid composition within experimental error. The fully reduced 75-kDa catalytic subunits of nondigested control enzyme appeared about 2 kDa larger than the corresponding subunits of disaggregated enzyme on polyacrylamide gel electrophoresis in sodium dodecyl sulfate, an indication that the hydrophobic domain was cleaved from the COOH or NH2 terminus of the catalytic subunit primary structure. Studies in which the NH-terminal amino acid was labeled by reductive methylation suggested that the hydrophobic domain is at the COOH terminus.
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M3 - Article
C2 - 6371009
AN - SCOPUS:0021329848
SN - 0021-9258
VL - 259
SP - 5653
EP - 5660
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 9
ER -