Identification of secretory vesicles in homogenates of pea stem segments |
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| Authors: | L. Taiz M. Murry D. G. Robinson |
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| Affiliation: | (1) Thimann Laboratories, Division of Natural Sciences, University of California, 95064 Santa Cruz, CA, USA;(2) Harvard Forest, 01366 Petersham, MA, USA;(3) Abteilung Cytologie, Pflanzenphysiologisches Institut der Universität, Untere Karspüle 2, D-3400 Göttingen, Germany |
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| 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,Mg2+-adenosine triphosphatase (pH 6.5), were not detected in secretory vesicles. Pulse-chase experiments with [3H]glucose support our designation of secretory vesicles and Golgi-cisternal fractions.Abbreviations ER endoplasmic reticulum - GSI, GSII glucan, synthase I, II, respectively - IDPase inosine diphosphatase - PM plasma membrane - SV(s) secretory vesicle(s) |
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| Keywords: | Glucan synthase Golgi apparatus Inosine diphosphatase Pisum, secretory vesicles Renografin gradient Secretory vesicle |
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