The Effect of Interactions Involving Ionizable Residues Flanking Membrane-Inserted Hydrophobic Helices upon Helix−Helix Interaction†

Biochemistry ◽  
2003 ◽  
Vol 42 (36) ◽  
pp. 10833-10842 ◽  
Author(s):  
Scott Lew ◽  
Gregory A. Caputo ◽  
Erwin London
Keyword(s):  
Hydrophobic Helices ◽  
Ionizable Residues

scholarly journals Distinctions between Hydrophobic Helices in Globular Proteins and Transmembrane Segments as Factors in Protein Sorting

2008 ◽  
Vol 284 (8) ◽  
pp. 5395-5402 ◽  
Author(s):  
Fiona Cunningham ◽  
Arianna Rath ◽  
Rachel M. Johnson ◽  
Charles M. Deber
Keyword(s):  
Protein Sorting ◽  
Globular Proteins ◽  
Transmembrane Segments ◽  
Hydrophobic Helices

scholarly journals Seipin traps triacylglycerols to facilitate their nanoscale clustering in the ER membrane

2020 ◽  
Author(s):  
Xavier Prasanna ◽  
Veijo T. Salo ◽  
Shiqian Li ◽  
Katharina Ven ◽  
Helena Vihinen ◽  
...  
Keyword(s):  
Lipid Droplet ◽  
In Silico ◽  
Lipid Membrane ◽  
Wild Type ◽  
Binding Interface ◽  
Biomolecular Simulations ◽  
Hydrophobic Helices ◽  
Tag Clustering ◽  
Er Membrane ◽  
In Cells

AbstractSeipin is a disk-like oligomeric ER protein important for lipid droplet (LD) biogenesis and triacylglycerol (TAG) delivery to growing LDs. Here we show through biomolecular simulations bridged to experiments that seipin can trap TAGs in the ER bilayer via the luminal hydrophobic helices of the protomers delineating the inner opening of the seipin disk. This promotes the nanoscale sequestration of TAGs at a concentration that by itself is insufficient to induce TAG clustering in a lipid membrane. We identify Ser166 in the α3 helix as a favored TAG occupancy site and show that mutating it compromises the ability of seipin complexes to sequester TAG in silico and to promote TAG transfer to LDs in cells. While seipin-S166D mutant colocalizes poorly with promethin, the association of nascent wild-type seipin complexes with promethin is promoted by TAGs. Together, these results suggest that seipin traps TAGs via its luminal hydrophobic helices, serving as a catalyst for seeding the TAG cluster from dissolved monomers inside the seipin ring, thereby generating a favorable promethin binding interface.

scholarly journals Uncovering pH-Dependent Transient States of Proteins with Buried Ionizable Residues

2014 ◽  
Vol 136 (24) ◽  
pp. 8496-8499 ◽  
Author(s):  
Garrett B. Goh ◽  
Elena N. Laricheva ◽  
Charles L. Brooks
Keyword(s):  
Transient States ◽  
Ph Dependent ◽  
Ionizable Residues

Lipid-destabilizing properties of the hydrophobic helices H8 and H9 from colicin E1

2007 ◽  
Vol 24 (5-6) ◽  
pp. 419-430 ◽  
Author(s):  
L. Lins ◽  
K. El Kirat ◽  
B. Charloteaux ◽  
C. Flore ◽  
V. Stroobant ◽  
...  
Keyword(s):  
Colicin E1 ◽  
Hydrophobic Helices

scholarly journals Pyruvate carboxylase catalysis of phosphate transfer between carbamoyl phosphate and ADP

1991 ◽  
Vol 273 (2) ◽  
pp. 443-448 ◽  
Author(s):  
P V Attwood ◽  
B D L A Graneri
Keyword(s):  
Active Site ◽  
Pyruvate Carboxylase ◽  
Reverse Reaction ◽  
Carbamoyl Phosphate ◽  
Acetyl Coa ◽  
Essential Requirement ◽  
Pyruvate Carboxylation ◽  
Ionizable Residues ◽  
Ph Profiles

In a reaction that is analogous to the phosphorylation of ADP from carboxyphosphate, pyruvate carboxylase catalyses the formation of ATP from carbamoyl phosphate and ADP at a rate that is about 0.3% of the pyruvate-carboxylation reaction and about 3% of the full reverse reaction. Acetyl-CoA stimulates the phosphorylation of ADP from carbamoyl phosphate but is not an essential requirement of the reaction. Mg2+ also stimulates the reaction, and in the range of Mg2+ concentrations considered the effect of V is much larger in the absence of acetyl-CoA than in its presence. Acetyl-CoA and Mg2+ may be acting in a co-operative way to stimulate the phosphorylation of ADP in a similar way to their effects on the pyruvate-carboxylation reaction. The phosphorylation of ADP by carbamoyl phosphate is also stimulated by the presence of biotin in the part of the active site where this reaction occurs, but again it is not absolutely required for the reaction to proceed. The pH profiles of the phosphorylation of ADP by carbamoyl phosphate indicate that there are at least two ionizable residues involved in the reaction, one of which probably has a role in the release of carbamate from the active site.

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