PDBsum entry 2wpy

Transcription

PDB id: 2wpy

Contents

Protein chain

33 a.a.

Metals

_CL ×2

Waters ×19

References listed in PDB file

Key reference

Title

A coiled-Coil motif that sequesters ions to the hydrophobic core.

Authors

M.D.Hartmann, O.Ridderbusch, K.Zeth, R.Albrecht, O.Testa, D.N.Woolfson, G.Sauer, S.Dunin-Horkawicz, A.N.Lupas, B.H.Alvarez.

Ref.

Proc Natl Acad Sci U S A, 2009, 106, 16950-16955. [DOI no: 10.1073/pnas.0907256106]

PubMed id

19805097

Abstract

Most core residues of coiled coils are hydrophobic. Occasional polar residues are thought to lower stability, but impart structural specificity. The coiled coils of trimeric autotransporter adhesins (TAAs) are conspicuous for their large number of polar residues in position d of the core, which often leads to their prediction as natively unstructured regions. The most frequent residue, asparagine (N@d), can occur in runs of up to 19 consecutive heptads, frequently in the motif [I/V]xxNTxx. In the Salmonella TAA, SadA, the core asparagines form rings of interacting residues with the following threonines, grouped around a central anion. This conformation is observed generally in N@d layers from trimeric coiled coils of known structure. Attempts to impose a different register on the motif show that the asparagines orient themselves specifically into the core, even against conflicting information from flanking domains. When engineered into the GCN4 leucine zipper, N@d layers progressively destabilized the structure, but zippers with 3 N@d layers still folded at high concentration. We propose that N@d layers maintain the coiled coils of TAAs in a soluble, export-competent state during autotransport through the outer membrane. More generally, we think that polar motifs that are both periodic and conserved may often reflect special folding requirements, rather than an unstructured state of the mature proteins.

Figure 3.
Superposition of 16 trimeric N@d layers of known structure, including 3 exemplars from this study as listed in Table S1, all coordinating chloride. In 6 cases the polar network is extended by Thr in e of the neighboring chain and in 7 cases by Asn or Asp in g of the same chain, all with the same geometry as in SadAK3, including the bridging water molecule. Dimeric, tetrameric, and 2 further trimeric instances are shown in Fig. S2.

Figure 5.
Sequence of synthetic peptides used in this work. The sequence of GCN4-p1 N16V was modified by mutating specific residues (highlighted in gray) to create V/IxxNxx and V/IxxNTxx motifs.