PMID- 9593749
OWN - NLM
STAT- MEDLINE
DCOM- 19980701
LR  - 20220309
IS  - 0021-9258 (Print)
IS  - 0021-9258 (Linking)
VI  - 273
IP  - 22
DP  - 1998 May 29
TI  - Direct interaction of a Ca2+-binding loop of synaptotagmin with lipid bilayers.
PG  - 13995-4001
AB  - Synaptotagmin 1 binds Ca2+ and membranes via its C2A-domain and plays an 
      essential role in excitation-secretion coupling. In this study, we sought to 
      identify Ca2+- and membrane-induced local conformational changes in the 
      C2A-domain of synaptotagmin and to delineate the C2A-lipid binding interface. To 
      address these questions native phenylalanine residues were replaced, at each face 
      of the domain, with tryptophan reporters. Changes in tryptophanyl fluorescence 
      indicated that Ca2+ induced long range conformational changes throughout C2A, 
      including regions distant from an established Ca2+-binding site. Addition of 
      liposomes resulted in Ca2+-dependent increases in the fluorescence of tryptophans 
      193, 231, and 234. Only the tryptophan residues at positions 234 and 231, which 
      lie within a Ca2+-binding loop of C2A, exhibited liposome-induced blue shifts in 
      their emission spectra. Quenching experiments, using membrane-imbedded doxyl spin 
      labels, revealed that tryptophan residues 231 and 234 penetrated lipid bilayers. 
      These data delineate the lipid binding interface of C2A and provide the first 
      evidence for adjacent Ca2+- and lipid-binding sites within a C2-domain. The 
      penetration of C2A into membranes may function to bring components of the fusion 
      machinery into contact with the lipid bilayer to initiate exocytosis.
FAU - Chapman, E R
AU  - Chapman ER
AD  - Department of Physiology, University of Wisconsin School of Medicine, Madison, 
      Wisconsin 53706, USA. erchapma@facstaff.wisc.edu
FAU - Davis, A F
AU  - Davis AF
LA  - eng
GR  - GM 56827-01/GM/NIGMS NIH HHS/United States
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
PT  - Research Support, U.S. Gov't, P.H.S.
PL  - United States
TA  - J Biol Chem
JT  - The Journal of biological chemistry
JID - 2985121R
RN  - 0 (Calcium-Binding Proteins)
RN  - 0 (Lipid Bilayers)
RN  - 0 (Membrane Glycoproteins)
RN  - 0 (Nerve Tissue Proteins)
RN  - 0 (Recombinant Proteins)
RN  - 0 (Synaptotagmin I)
RN  - 0 (Syt1 protein, rat)
RN  - 134193-27-4 (Synaptotagmins)
RN  - SY7Q814VUP (Calcium)
SB  - IM
MH  - Animals
MH  - Calcium/*metabolism
MH  - Calcium-Binding Proteins/*metabolism
MH  - *Lipid Bilayers
MH  - Membrane Fusion
MH  - Membrane Glycoproteins/genetics/*metabolism
MH  - Mutagenesis, Site-Directed
MH  - Nerve Tissue Proteins/genetics/*metabolism
MH  - Rats
MH  - Recombinant Proteins/genetics/metabolism
MH  - Synaptotagmin I
MH  - Synaptotagmins
EDAT- 1998/06/05 00:00
MHDA- 1998/06/05 00:01
CRDT- 1998/06/05 00:00
PHST- 1998/06/05 00:00 [pubmed]
PHST- 1998/06/05 00:01 [medline]
PHST- 1998/06/05 00:00 [entrez]
AID - S0021-9258(19)57851-6 [pii]
AID - 10.1074/jbc.273.22.13995 [doi]
PST - ppublish
SO  - J Biol Chem. 1998 May 29;273(22):13995-4001. doi: 10.1074/jbc.273.22.13995.