The target-SNARE syntaxin 1A is an essential component of the core machinery required for regulated exocytosis (where SNARE is the soluble N-ethylmaleimide-sensitive fusion protein-attachment protein receptor). Syntaxin 1A interacts with a variety of other proteins, two of which, N-ethylmaleimide-sensitive fusion protein (NSF) and α-soluble NSF attachment protein (α-SNAP) have been suggested to impart a conformational rearrangement on this protein during a reaction referred to as priming. We have studied the effect of the primed state on the binding properties of syntaxin 1A and we have confirmed that primed syntaxin 1A no longer associated with α-SNAP or its cognate vesicle-SNARE, vesicle-associated membrane protein (VAMP). Under such conditions, however, it retained the ability to bind to nSec-1. It has been demonstrated that nSec-1, a regulatory protein also involved in neuronal exocytosis, binds syntaxin 1A with high affinity in vitro, although evidence for this physical interaction occurring in vivo has proven elusive. We analysed the subcellular distribution of these two proteins in fractions from bovine adrenal medulla and detected syntaxin 1A and nSec-1 in both plasma membrane and chromaffin-granule fractions. Using a cross-linking approach with chromaffin-granule membranes we detected a putative dimeric complex composed of approx. 54% total granule membrane nSec-1 and approx. 30% total syntaxin 1A. The results of this study therefore suggest the possibility of nSec-1 interactions with primed syntaxin 1A and demonstrate a potentially significant interaction of syntaxin 1A and nSec-1 on the membranes of chromaffin granules.
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Research Article|
September 05 1999
nSec-1 (munc-18) interacts with both primed and unprimed syntaxin 1A and associates in a dimeric complex on adrenal chromaffin granules
Lee P. HAYNES;
Lee P. HAYNES
1The Physiological Laboratory, University of Liverpool, Crown Street, Liverpool L69 3BX, U.K.
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Alan MORGAN;
Alan MORGAN
1The Physiological Laboratory, University of Liverpool, Crown Street, Liverpool L69 3BX, U.K.
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Robert D. BURGOYNE
Robert D. BURGOYNE
1
1The Physiological Laboratory, University of Liverpool, Crown Street, Liverpool L69 3BX, U.K.
1To whom correspondence should be addressed (e-mail burgoyne@liverpool.ac.uk).
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Publisher: Portland Press Ltd
Received:
May 17 1999
Revision Received:
June 29 1999
Accepted:
July 13 1999
Online ISSN: 1470-8728
Print ISSN: 0264-6021
The Biochemical Society, London © 1999
1999
Biochem J (1999) 342 (3): 707–714.
Article history
Received:
May 17 1999
Revision Received:
June 29 1999
Accepted:
July 13 1999
Citation
Lee P. HAYNES, Alan MORGAN, Robert D. BURGOYNE; nSec-1 (munc-18) interacts with both primed and unprimed syntaxin 1A and associates in a dimeric complex on adrenal chromaffin granules. Biochem J 15 September 1999; 342 (3): 707–714. doi: https://doi.org/10.1042/bj3420707
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