
Chemical modification of charged amino acid moieties alters the electrophoretic mobilities of neurofilament subunits on SDS/polyacrylamide gels
Author(s) -
GEORGES Elias,
MUSHYNSKI Walter E.
Publication year - 1987
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1987.tb11439.x
Subject(s) - neurofilament , dephosphorylation , protein subunit , biochemistry , electrophoresis , polyacrylamide gel electrophoresis , chemistry , amino acid , lysine , gel electrophoresis , phosphorylation , biology , enzyme , phosphatase , immunohistochemistry , gene , immunology
The increase in the mobilities of neurofilament subunits on SDS‐PAGE after dephosphorylation was reversed upon boiling in urea or trifluoroacetylation of lysine ɛ‐amino groups. Trifluoroacetylation of native and dephosphorylated neurofilaments also resulted in an overall increase in the phosphorylation of the three subunits by the catalytic subunit of cyclic‐AMP‐dependent protein kinase. The gel‐electrophoretic mobility of neurofilament subunits was also shown to be influenced by carboxylic amino acid residues, as neutralization of these moieties by glycinamidation increased the mobilities of all three subunits on SDS‐PAGE. Neurofilament subunits that were both glycinamidated and dephosphorylated had apparent molecular masses of approximately 60 kDa, 112 kDa and 138 kDa. The major sites of these changes in the two largest subunits were shown to be the carboxy‐terminal tail domains, which are known to contain high percentages of glutamate. Since interspecies differences in the apparent molecular masses of neurofilament subunits were shown to persist after glycinamidation and dephosphorylation, they appear to be due to differences in polypeptide chain length, rather than glutamate content.