Limits...
Molecular design principles underlying β-strand swapping in the adhesive dimerization of cadherins.

Vendome J, Posy S, Jin X, Bahna F, Ahlsen G, Shapiro L, Honig B - Nat. Struct. Mol. Biol. (2011)

Bottom Line: We show that strand swapping in EC1 is driven by conformational strain in cadherin monomers that arises from the anchoring of their short N-terminal strand at one end by the conserved Trp2 and at the other by ligation to Ca(2+) ions.We also demonstrate that a conserved proline-proline motif functions to avoid the formation of an overly tight interface where affinity differences between different cadherins, crucial at the cellular level, are lost.We use these findings to design site-directed mutations that transform a monomeric EC2-EC3 domain cadherin construct into a strand-swapped dimer.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry and Molecular Biophysics, Columbia University, New York, New York, USA. Center for Computational Biology and Bioinformatics, Columbia University, New York, New York, USA. Howard Hughes Medical Institute, Columbia University, New York, New York, USA.

ABSTRACT
Cell adhesion by classical cadherins is mediated by dimerization of their EC1 domains through the 'swapping' of N-terminal β-strands. We use molecular simulations, measurements of binding affinities and X-ray crystallography to provide a detailed picture of the structural and energetic factors that control the adhesive dimerization of cadherins. We show that strand swapping in EC1 is driven by conformational strain in cadherin monomers that arises from the anchoring of their short N-terminal strand at one end by the conserved Trp2 and at the other by ligation to Ca(2+) ions. We also demonstrate that a conserved proline-proline motif functions to avoid the formation of an overly tight interface where affinity differences between different cadherins, crucial at the cellular level, are lost. We use these findings to design site-directed mutations that transform a monomeric EC2-EC3 domain cadherin construct into a strand-swapped dimer.

Show MeSH

Related in: MedlinePlus

Modulation of the effect of Ca2+ on the A*/A strand mobility by the W2F mutation. The graph presents the difference between the R.m.s.f. observed in presence of Ca2+ and the R.m.s.f. observed in absence of Ca2+ for the E-cadherin wild-type (blue) and W2F mutant (orange) closed monomer sets of simulations.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3113550&req=5

Figure 4: Modulation of the effect of Ca2+ on the A*/A strand mobility by the W2F mutation. The graph presents the difference between the R.m.s.f. observed in presence of Ca2+ and the R.m.s.f. observed in absence of Ca2+ for the E-cadherin wild-type (blue) and W2F mutant (orange) closed monomer sets of simulations.

Mentions: Our model implies that both anchor points are required simultaneously to induce strain in the A*/A strand which would, otherwise, be able to assume a more relaxed conformation. In order to further computationally test this hypothesis, we carried out simulations on the closed conformation of the E-cadherin W2F mutant. Note that in the apo state the A*/A strand in the W2F mutant undergoes larger fluctuations than wild type (Supplementary Fig. 4) but that in the Ca2+-bound state the fluctuations are of comparable magnitude. Figure 4 plots the difference in R.m.s.f. between the Ca2+-bound state and apo state of both the wild-type and the W2F mutant. It is clear from the figure that Ca2+ binding has only limited effect on the mobility of the A*/A strand in the mutant. These results suggest a coupling in the wild type protein between the N- and C-termini, which are located more than 25 Å apart. This coupling is absent in the W2F mutant which we interpret as a reduction in constraints due to the loss of a hydrogen bond between the NH group of Trp2 side chain and the carboxyl group of Asp90 and to the smaller Phe2 side chain which poses fewer conformational constraints than the indole ring of Trp2 (Supplementary Fig. 5 and Supplementary Fig. 4). The simulations also show that the W2F mutant <dist2-11> ≈ 25.5Ǻ, in both the Ca2+ bound and Ca2+ free states so that the Ca2+ induced elongation of the mutant A*/A strand has disappeared (Supplementary Fig. 3a).


Molecular design principles underlying β-strand swapping in the adhesive dimerization of cadherins.

Vendome J, Posy S, Jin X, Bahna F, Ahlsen G, Shapiro L, Honig B - Nat. Struct. Mol. Biol. (2011)

Modulation of the effect of Ca2+ on the A*/A strand mobility by the W2F mutation. The graph presents the difference between the R.m.s.f. observed in presence of Ca2+ and the R.m.s.f. observed in absence of Ca2+ for the E-cadherin wild-type (blue) and W2F mutant (orange) closed monomer sets of simulations.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3113550&req=5

Figure 4: Modulation of the effect of Ca2+ on the A*/A strand mobility by the W2F mutation. The graph presents the difference between the R.m.s.f. observed in presence of Ca2+ and the R.m.s.f. observed in absence of Ca2+ for the E-cadherin wild-type (blue) and W2F mutant (orange) closed monomer sets of simulations.
Mentions: Our model implies that both anchor points are required simultaneously to induce strain in the A*/A strand which would, otherwise, be able to assume a more relaxed conformation. In order to further computationally test this hypothesis, we carried out simulations on the closed conformation of the E-cadherin W2F mutant. Note that in the apo state the A*/A strand in the W2F mutant undergoes larger fluctuations than wild type (Supplementary Fig. 4) but that in the Ca2+-bound state the fluctuations are of comparable magnitude. Figure 4 plots the difference in R.m.s.f. between the Ca2+-bound state and apo state of both the wild-type and the W2F mutant. It is clear from the figure that Ca2+ binding has only limited effect on the mobility of the A*/A strand in the mutant. These results suggest a coupling in the wild type protein between the N- and C-termini, which are located more than 25 Å apart. This coupling is absent in the W2F mutant which we interpret as a reduction in constraints due to the loss of a hydrogen bond between the NH group of Trp2 side chain and the carboxyl group of Asp90 and to the smaller Phe2 side chain which poses fewer conformational constraints than the indole ring of Trp2 (Supplementary Fig. 5 and Supplementary Fig. 4). The simulations also show that the W2F mutant <dist2-11> ≈ 25.5Ǻ, in both the Ca2+ bound and Ca2+ free states so that the Ca2+ induced elongation of the mutant A*/A strand has disappeared (Supplementary Fig. 3a).

Bottom Line: We show that strand swapping in EC1 is driven by conformational strain in cadherin monomers that arises from the anchoring of their short N-terminal strand at one end by the conserved Trp2 and at the other by ligation to Ca(2+) ions.We also demonstrate that a conserved proline-proline motif functions to avoid the formation of an overly tight interface where affinity differences between different cadherins, crucial at the cellular level, are lost.We use these findings to design site-directed mutations that transform a monomeric EC2-EC3 domain cadherin construct into a strand-swapped dimer.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry and Molecular Biophysics, Columbia University, New York, New York, USA. Center for Computational Biology and Bioinformatics, Columbia University, New York, New York, USA. Howard Hughes Medical Institute, Columbia University, New York, New York, USA.

ABSTRACT
Cell adhesion by classical cadherins is mediated by dimerization of their EC1 domains through the 'swapping' of N-terminal β-strands. We use molecular simulations, measurements of binding affinities and X-ray crystallography to provide a detailed picture of the structural and energetic factors that control the adhesive dimerization of cadherins. We show that strand swapping in EC1 is driven by conformational strain in cadherin monomers that arises from the anchoring of their short N-terminal strand at one end by the conserved Trp2 and at the other by ligation to Ca(2+) ions. We also demonstrate that a conserved proline-proline motif functions to avoid the formation of an overly tight interface where affinity differences between different cadherins, crucial at the cellular level, are lost. We use these findings to design site-directed mutations that transform a monomeric EC2-EC3 domain cadherin construct into a strand-swapped dimer.

Show MeSH
Related in: MedlinePlus