Biochemical characterization of a neuroserpin variant associated with hereditary dementia

Neuroserpin isolated from inclusion bodies in the brain. of a patient with a neurodegenerative disease was characterized biochemically, The protein co nsisted of residues 20 to 410 of the neuroserpin precursor deduced from its cDNA sequence indicating the entire molecule was deposited. A minor amount started with residue 19 of the precursor, and the carboxyl terminus was he terogeneous ending at residues 405, 407, 409, and 410. Arg was present at p osition 52, No normal Ser52 was found indicating that only mutant neuroserp in was present in the inclusion bodies. The three potential Asn glycosylati on sites all contained carbohydrate, DNA sequence analysis of exons 2 to 19 of the neuroserpin gene in the proband showed the published normal neurose rpin sequence except for the presence of both adenine and cytosine at the f irst position of codon 52, that indicates heterozygosity for both the norma l Ser(AGT) and variant Arg(CGT) at this position in the expressed protein, Restriction fragment length polymorphism analysis of a polymerase chain rea ction product from exon 2 revealed the propositus and his affected sibling both were heterozygous for the mutation whereas 100 unaffected controls wer e negative, Chemical characterization of the variant neuroserpin will signi ficantly enhance the understanding of this protein in both normal physiolog y and neurodegenerative diseases.