Proposed role of the alpha subunit of the 7 S nerve growth factor protein: implications for the regulation of NGF activity.

Four electrophoretically distinct alpha subunits can be isolated from mouse 7 S nerve growth factor protein (7 S NGF). It is proposed that each alpha subunit confers on its 7 S NGF species a different dissociation constant, and that the heterogeneity in dissociation constants of the different 7 S NGF species provide a mechanism for regulating the structure of betaNGF. A hypothesis that the different betaNGF structures have altered receptor affinities and/or physiological properties which can functionally differentiate NGF activity is also presented.