The high molecular weight nerve growth factor complex from Mastomys natalensis differs from the murine nerve growth factor complex

Abstract

Both the male and the female of Mastomys natalensis, an African rat, have high levels of nerve growth factor (NGF) in their submaxillary glands. Mastomys high molecular weight (HMW) NGF was purified by gel filtration and ion-exchange chromatography and was compared with HMW NGF from the male mouse submaxillary gland. Mastomys HMW NGF sediments as a 5S species, does not exhibit esterase activity, and is more difficult to dissociate at acid pH than mouse 7S NGF. The biological activity could be isolated as a purified Mastomys beta NGF protein identical in size and charge with that purified from male mice. The N-terminal amino acid sequence of the first 20 residues was determined and found to differ from that of mouse only at residue 8. Western blotting of Mastomys 5S NGF using antiserum against mouse beta NGF indicates that the beta NGF subunit of Mastomys is very similar to that of the mouse. Southern blots using a mouse kallikrein probe also demonstrate the presence of a large kallikrein family in Mastomys similar to that in mouse, and Northern blots verify transcription of kallikreins in Mastomys submaxillary gland. SDS-PAGE and isoelectric focusing gels reveal a Mastomys subunit that comigrates with mouse alpha subunit. However, neither oligonucleotide probes directed against mouse alpha subunit RNA nor antibodies directed against mouse alpha NGF cross-react strongly with the Mastomys material. This indicates that the second subunit of the Mastomys complex is not very similar to the mouse alpha subunit.