Characterization of three neurosecretory proteins from the A median neurosecretory cells of Locusta migratoria by coupled chromatographic,electrophoretic and isoelectrofocusing methods

Proteins from the nervous corpora cardiaca (N-CC) of Locusta migratoria were analysed using a combination of chromatography, electrophoresis and electrofocusing. Three major cysteine or/and cystine-rich proteins were identified as neurosecretory proteins of the median neurosecretory cells (M-NSC) by comparing the pattern of separated proteins of (1) intact N-CC and (2) depleted N-CC after intracerebral axotomy of the M-NSC.These three neurosecretory proteins are: a trimer, a dimer and a monomer. The trimer and the monomer are composed of apparent 18,000 subunits and 9000 polypeptide chains. The dimer is composed of apparent 7000 subunits composed of putative 4000 polypeptide chains. The three neurosecretory proteins are acidic (pH_i approx. 5.6 for the trimer, 5.1 for the monomer and 4.0 for the dimer). Their relationship to the neurophysins and to the neurosecretory protein isolated from brain and corpora cardiaca of the locust by Friedel et al. (1980) (Gen. comp. Endocr.41, 487–498) is discussed. The role of these three neurosecretory proteins (carrier protein, neurohormone or precursor of neurohormone) is as yet unknown.