Dissecting the thermodynamic contributions of the charged residues in the membrane anchoring of Bcl-xl C-terminal domain

Bcl-2 Family Members and the Mitochondrial Import Machineries: The Roads to Death

“…Note that similar selectivity experiments have been done with these C-terminal sequences fused to GFP with similar results, suggesting that the information required was indeed entirely present in this C-terminal domain. A thermodynamic study indicated that the two positive charges flanking the N-side of the α-helix of Bcl-xL might not be crucial for membrane anchoring but might be required for an adequate orientation of the helix within the membrane [ 56 ].…”

Shifting Polar Residues Across Primary Sequence Frames of Transmembrane Domains Calibrates Membrane Permeation Thermodynamics

“…Consideration of this RC was critical around the water-bilayer interface, where the peptide prefers the horizontal orientation, and as the peptide goes deeper into the bilayer, it reorients to the vertical orientation. 15,35 So to build the 2D PMF, 5−9 continuous bins along "DIST-Z" (bins that represent partially inserted states of the peptide) and seven nonoverlapping bins along "TLT" Study of BXCT at a High P:L Ratio. To make the anionic bilayer surface crowded with BXCT, three peptides were placed around the center of the bilayer surface one-by-one with subsequent equilibrium simulations on each addition, in an attempt to cause surface charge neutralization and subsequent deformation to the bilayer.…”

“…The choice of RC is very crucial as it should clearly differentiate the final states of interest, as well as require to sufficiently sample the rarely visited transition states . Biological processes are often associated with “hidden barriers” across a slower degrees of freedom, e.g., transition of a peptide into a bilayer is often associated with peptide rotation. , However, devising an ideal RC that can describe the complexity of transition states is often not trivial and subject to rigorous independent investigation, e.g., RC for pore formation inside a membrane bilayer. , In such cases, considering more than one RC, representing the relevant degrees of freedom, can provide a better insight of the process compared to a single RC. In the present investigation, a combination of 1D (i.e.…”

“…Using computational approaches, Maity et al have also shown that the membrane penetration capacity of the R232A-K233A double mutant was severely abrogated compared to the wild-type Bcl-xL CTA peptide. 15 They have also suggested a redundancy of positively charged residues at the C-terminus in terms of driving the membrane insertion, and such redundancy in the primary sequence of the CTA region is also witnessed in several other Bcl-2 family members, e.g., Bak, Mcl-1, Bcl-W, etc. 8 So, if the presence of charged residues at the tip of the CTA region is the rudimentary criteria for its insertion, then the deviation of that policy in the case of the Bax CTA ( 169 TWQTVTIFVAGVLTASLTIWKKMG 192 ) is indeed intriguing.…”

“…The MOM targeting sequences of the Bcl-2 family of proteins are generally ∼20 residues long transmembrane domains flanked by basic amino acids. , It has been shown by Jeong et al that truncation of the Bcl-xL CTA region ( 209 RFN­RWF­LTG­MTV­AGV­VLL­GSL­FS­RK 233 ), by four or five residues from the C-terminus end (termed as Δ4C or Δ5C, respectively), completely incapacitates the peptide to penetrate the membrane which has no difference with a 229 AAAAA 233 mutant (i.e., five C-terminal residues are mutated to Ala). Using computational approaches, Maity et al have also shown that the membrane penetration capacity of the R232A-K233A double mutant was severely abrogated compared to the wild-type Bcl-xL CTA peptide . They have also suggested a redundancy of positively charged residues at the C-terminus in terms of driving the membrane insertion, and such redundancy in the primary sequence of the CTA region is also witnessed in several other Bcl-2 family members, e.g., Bak, Mcl-1, Bcl-W, etc .…”