The structure and organization of the human heavy neurofilament subunit (NF‐H) and the gene encoding it

• Published in: The EMBO journal 1988-07, Vol.7 (7), p.1947-1955
• Main Authors: Lees, J. F., Shneidman, P. S., Skuntz, S. F., Carden, M. J., Lazzarini, R. A.
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Base Sequence; Biological and medical sciences; Cloning, Molecular; DNA - isolation & purification; Exons; Fundamental and applied biological sciences. Psychology; Genes; Genes. Genome; Humans; Intermediate Filament Proteins - genetics; Introns; Macromolecular Substances; Molecular and cellular biology; Molecular genetics; Molecular Sequence Data; Neurofilament Proteins; Protein Conformation; Sequence Homology, Nucleic Acid
• ISSN: 0261-4189; 1460-2075
• DOI: 10.1002/j.1460-2075.1988.tb03032.x

Genomic clones for the largest human neurofilament protein (NF‐H) were isolated, the intron/exon boundaries mapped and the entire protein‐coding regions (exons) sequenced. The predicted protein contains a central region that obeys the structural criteria identified for alpha‐helical ‘rod’ domains typically present in all IF protein components: it is approximately 310 amino acids long, shares amino acid sequence homology with other IF protein rod domains and displays the characteristic heptad repeats of apolar amino acids which facilitate coiled‐coil interaction. Nevertheless, anomalies are noted in the structure of the NF‐H rod which could explain observations of its poor homopolymeric assembly in vitro. The protein segment on the carboxy‐terminal side of the human NF‐H rod is uniquely long (greater than 600 amino acids) compared to other IF proteins and is highly charged (greater than 24% Glu, greater than 25% Lys), rich in proline (greater than 12%) and impoverished in cysteine, methionine and aromatic amino acids. Its most remarkable feature is a repetitive sequence that covers more than half its length and includes the sequence motif, Lys‐Ser‐Pro (KSP) greater than 40 times. Together with the recent identification of the serine in KSP as the main target for NF‐directed protein kinases in vivo, this repetitive character explains the massive phosphorylation of the NF‐H subunit that can occur in axons. The human NF‐H gene has three introns, two of which interrupt the protein‐coding sequence at identical points to introns in the genes for the two smaller NF proteins, NF‐M and NF‐L.