scholarly journals Shedding of hyaluronate synthase from streptococci

1990 ◽  
Vol 267 (1) ◽  
pp. 191-196 ◽  
Author(s):  
A Mausolf ◽  
J Jungmann ◽  
H Robenek ◽  
P Prehm
Keyword(s):  
Membrane Protein ◽  
Protease Inhibitors ◽  
Chain Length ◽  
Sedimentation Rate ◽  
Culture Medium ◽  
Integral Membrane Protein ◽  
Phospholipid Vesicles ◽  
Free Solution ◽  
Hyaluronate Synthase

Hyaluronate synthase was shed into the culture medium from growing streptococci (group C) together with nascent hyaluronate. The mechanism of solubilization was analysed using isolated protoplast membranes. Solubilization increased when membranes were suspended in larger volumes, but it was temperature-independent and was not inhibited by protease inhibitors. Increased hyaluronate chain length enhanced solubilization. The soluble synthase could re-integrate into Streptococcal membranes in a saturable manner. The soluble synthase behaved like an integral membrane protein, although it was not integrated into phospholipid vesicles. In sucrose velocity centrifugation the synthase had a higher sedimentation rate in detergent-free solution, indicating that it existed in an aggregated state.

scholarly journals Human meprinbeta: O-linked glycans in the intervening region of the type I membrane protein protect the C-terminal region from proteolytic cleavage and diminish its secretion

2003 ◽  
Vol 369 (3) ◽  
pp. 659-665 ◽  
Author(s):  
Boris LEUENBERGER ◽  
Dagmar HAHN ◽  
Anastassios PISCHITZIS ◽  
Marianne K. HANSEN ◽  
Erwin E. STERCHI
Keyword(s):  
Membrane Protein ◽  
Brush Border ◽  
Culture Medium ◽  
Brush Border Membrane ◽  
Integral Membrane Protein ◽  
Proteolytic Processing ◽  
Type I ◽  
Β Subunit ◽  
Α Subunit ◽  
Small Intestinal

Human meprin (hmeprin; N-benzoyl-l-tyrosyl-p-aminobenzoic acid hydrolase; EC 3.4.24.18) is a member of the astacin family of zinc metalloendopeptidases. The major site of expression is the brush border membrane of small intestinal and kidney epithelial cells. The enzyme is a type I integral membrane protein composed of two distinct subunits, α and β, which are linked by disulphide bridges. The enzyme complex is attached to the plasma membrane only via the β-subunit. The α-subunit is cleaved in the endoplasmic reticulum in a constitutive manner to remove the C-terminal membrane anchor which leads to secretion of the protein. While the β-subunit of hmeprin remains largely attached to the brush-border membrane some proteolytic processing occurs intracellularly as well as at the cell surface and results in the release of this subunit from the cell. In the present paper, we report that the β-subunit bears multiple O-linked sugar residues in the intervening domain. In contrast, the α-subunit does not contain O-linked oligosaccharides. Our results show that the O-linked carbohydrate side chains in hmeprinβ are clustered around a 13 amino acid sequence that contains the main cleavage site for proteolytic processing of the subunit. Prevention of O-glycosylation by specific inhibitors leads to enhanced proteolytic processing and the consequence is an increased release of hmeprinβ into the culture medium.

scholarly journals Predicting the Structure and Dynamics of Membrane Protein GerAB from Bacillus subtilis

2021 ◽  
Vol 22 (7) ◽  
pp. 3793
Author(s):  
Sophie Blinker ◽  
Jocelyne Vreede ◽  
Peter Setlow ◽  
Stanley Brul
Keyword(s):  
Bacillus Subtilis ◽  
Membrane Protein ◽  
Spore Germination ◽  
Structural Information ◽  
Transmembrane Protein ◽  
Homology Modelling ◽  
Water Channel ◽  
Md Simulations ◽  
Integral Membrane Protein ◽  
Starting Point

Bacillus subtilis forms dormant spores upon nutrient depletion. Germinant receptors (GRs) in spore’s inner membrane respond to ligands such as L-alanine, and trigger spore germination. In B. subtilis spores, GerA is the major GR, and has three subunits, GerAA, GerAB, and GerAC. L-Alanine activation of GerA requires all three subunits, but which binds L-alanine is unknown. To date, how GRs trigger germination is unknown, in particular due to lack of detailed structural information about B subunits. Using homology modelling with molecular dynamics (MD) simulations, we present structural predictions for the integral membrane protein GerAB. These predictions indicate that GerAB is an α-helical transmembrane protein containing a water channel. The MD simulations with free L-alanine show that alanine binds transiently to specific sites on GerAB. These results provide a starting point for unraveling the mechanism of L-alanine mediated signaling by GerAB, which may facilitate early events in spore germination.

Crystallization and preliminary X-ray analysis of ferric enterobactin receptor FepA, an integral membrane protein fromEscherichia coli

1998 ◽  
Vol 54 (4) ◽  
pp. 697-699 ◽  
Author(s):  
Barbara S. Smith ◽  
Bostjan Kobe ◽  
Ravi Kurumbail ◽  
Susan K. Buchanan ◽  
Lalitha Venkatramani ◽  
...  
Keyword(s):  
Membrane Protein ◽  
Integral Membrane Protein ◽  
X Ray ◽  
Fromescherichia Coli
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