Identification of previously unrecognized sequence motifs at the extreme carboxyterminus of the neurofilament subunit NF-M.

Two previously unrecognized features of neurofilament architecture are revealed by careful analysis of published neurofilament sequences. 1. The extreme C-terminus of the NF-M tail contains two highly conserved homologous sequences each of 15 amino acids, with the consensus EEK-V-TKKVEK-TS, plus another very closely related 7 amino acid sequence. 2. The C-terminus of NF-M contains sequences of consensus K-SP or K--SP which in some species are multiply repeated, are probably phosphorylated, but are distinct from the more obvious KSP repeated sequences. Sequences related to both the K-SP and K--SP sequences are found in NF-H, microtubule associated proteins tau and MAP2, suggesting a further level of immunological and potential evolutionary relationship between neurofilaments and these microtubule associated proteins. The possible significance of these findings is discussed.