Mouse 7S nerve growth factor: complete sequence of a cDNA coding for the alpha-subunit precursor and its relationship to serine proteases.

Abstract

Two synthetic oligonucleotides, one 14-mer and one 15-mer, each containing 32 sequences and corresponding to two regions of the partially determined protein sequence, were utilized to identify three cDNA clones coding for the precursor of the alpha-subunit of 7S mouse nerve growth factor (NGF). This library, containing 860 clones, had been preselected from a much larger one by low-stringency hybridization using a cDNA probe corresponding to one of the large family of glandular kallikreins expressed in the adult male mouse submandibular gland. Partial sequence analysis had previously established the alpha-subunit to be a member of this group, albeit with no demonstrable catalytic activity. Nucleotide sequence analysis of the longest of these clones (2A4) predicted the apparent complete amino acid sequence of the 265-residue precursor. One of the other clones (3F2) contained an A----G substitution at position 565 resulting in a Lys----Glu change at position 160 of the mature sequence. These clones probably represent two different alleles. Several amino acid changes, relative to other serine proteases, are evident, which may account for the apparent lack of enzymatic activity. An Arg----Gln substitution at residue -1 would prevent cleavage of the putative activation peptide, and the deletion of residues 2-5 interrupts the highly conserved Ile/Val-Ile/Val-Gly-Gly N-terminal sequence. An Asp----Tyr substitution in the binding pocket and a Gly----His substitution near the active site serine also probably contribute to the inactive structure. The role of this subunit in NGF function remains obscure.