Crosslinking of microsomal proteins identifies P-9000, a protein that is co-transported with phaseolin and phytohemagglutinin in bean cotyledons |
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Authors: | Michael A Tanchak Maarten J Chrispeels |
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Institution: | (1) Department of Biology, University of California/San Diego, 92093-0116 La Jolla, CA, USA;(2) Present address: Department of Biochemistry, University of Ottawa, 30 George Glinski, K1N 6N5 Ottawa, Ont., Canada |
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Abstract: | Developing cotyledons of the common bean, Phaseolus vulgaris L., transport within their secretory system (endoplasmic reticulum and Golgi apparatus) the abundant vacuolar proteins, phaseolin and phytohemagglutinin. To identify proteins that may play a role in vacuolar targeting, we treated cotyledon microsomal fractions with a bifunctional crosslinking reagent, dithiobis(succinimidyl propionate), isolated protein complexes with antibodies to phaseolin and phytohemagglutinin, and analysed the polypeptides by sodium dodecylsulfate polyacrylamide gel electrophoresis. This allowed us to identify a protein of Mr=9000 (P-9000) that was crosslinked to both phaseolin and phytohemagglutinin. P-900 is abundantly present in the endoplasmic reticulum. The aminoterminus of P-9000 shows extensive sequence identity with the amino-terminus of PA1 (Mr=11 000), a cysteine-rich albumin whose processing products accumulate in the vacuoles of pea (Pisum sativum L.) cotyledons. Like PA1, P-9000 is synthesized as a pre-proprotein that is posttranslationally processed into smaller polypeptides. The possible functions of P-9000 are discussed.Abbreviations DSP
dithiobis(succinimidyl propionate)
- EDTA
ethylenediaminetetraacetic acid
- ER
endoplasmic reticulum
- kDa
kilodalton
- Mr
relative molecular mass
- PHA
phytohemagglutinin
- SDS
sodium dodecylsulfate
- PAGE
polyacrylamide gel electrophoresis |
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Keywords: | Endoplasmic reticulum Phaseolus (protein complexes) Protein targeting Protein crosslinking Transport (protein) |
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