title: Identification of secretory vesicles in homogenates of pea stem segments.
abstract: In homogenates of stem sections from etiolated pea (Pisum sativum L.) seedlings, secretory vesicles can be separated from Golgi-apparatus cisternae by rate-zonal centrifugation in renografin gradients. Optically, two bands of turbidity are observed, the uppermost containing the secretory vesicles and the lower one the Golgi-apparatus cisternae. The absence of glutaraldehyde in the homogenizing medium has allowed the effective characterization of marker-enzyme activities. Golgi-apparatus cisternae have been recognized by the presence of inosine-diphosphatase and glucan-synthase I activities as well as by electron microscopy. In contrast, although secretory vesicles also bear inosine diphosphatase they do not appear to possess glucan-synthase activity. Three plasma-membrane markers, NPA-binding, glucan synthase II, and KCl,Mg(2+)-adenosine triphosphatase (pH 6.5), were not detected in secretory vesicles. Pulse-chase experiments with [(3)H]glucose support our designation of secretory vesicles and Golgi-cisternal fractions.
authors.affiliation: Thimann Laboratories, Division of Natural Sciences, University of California, 95064, Santa Cruz, CA, USA.
authors.forename: L
authors.initials: L
authors.lastname: Taiz
authors.forename: M
authors.initials: M
authors.lastname: Murry
authors.forename: D G
authors.initials: DG
authors.lastname: Robinson