PDBsum entry 3kih

Sugar binding protein

PDB id: 3kih

Contents

Protein chains

90 a.a. *

95 a.a. *

Ligands

GDL ×4

Waters ×6

* Residue conservation analysis

PDB id:

3kih

Name:

Sugar binding protein

Title:

The crystal structures of two fragments truncated from 5-bladed beta- propeller lectin, tachylectin-2 (lib2-d2-15)

Structure:

5-bladed beta-propeller lectin. Chain: a, b, c, d, e. Fragment: residues 1-97. Synonym: tachylectin-2. Engineered: yes

Source:

Synthetic construct. Organism_taxid: 32630. Expressed in: escherichia coli. Expression_system_taxid: 562.

Resolution:

2.49Å R-factor: 0.237 R-free: 0.299

Authors:

O.Dym,D.S.Tawfik,I.Yadid,Israel Structural Proteomics Center (Ispc)

Key ref:

I.Yadid et al. (2010). Metamorphic proteins mediate evolutionary transitions of structure. Proc Natl Acad Sci U S A, 107, 7287-7292. PubMed id: 20368465

Date:

02-Nov-09 Release date: 28-Apr-10

Protein chains

Q27084  (TAL2_TACTR) -  Tachylectin-2 from Tachypleus tridentatus

Seq: 255 a.a.

Struc: 90 a.a.*

Protein chains

Q27084  (TAL2_TACTR) -  Tachylectin-2 from Tachypleus tridentatus

Seq: 255 a.a.

Struc: 95 a.a.*

* PDB and UniProt seqs differ at 6 residue positions (black crosses)

Proc Natl Acad Sci U S A 107:7287-7292 (2010)

PubMed id: 20368465

Metamorphic proteins mediate evolutionary transitions of structure.

I.Yadid, N.Kirshenbaum, M.Sharon, O.Dym, D.S.Tawfik.

ABSTRACT

The primary sequence of proteins usually dictates a single tertiary and quaternary structure. However, certain proteins undergo reversible backbone rearrangements. Such metamorphic proteins provide a means of facilitating the evolution of new folds and architectures. However, because natural folds emerged at the early stages of evolution, the potential role of metamorphic intermediates in mediating evolutionary transitions of structure remains largely unexplored. We evolved a set of new proteins based on approximately 100 amino acid fragments derived from tachylectin-2--a monomeric, 236 amino acids, five-bladed beta-propeller. Their structures reveal a unique pentameric assembly and novel beta-propeller structures. Although identical in sequence, the oligomeric subunits adopt two, or even three, different structures that together enable the pentameric assembly of two propellers connected via a small linker. Most of the subunits adopt a wild-type-like structure within individual five-bladed propellers. However, the bridging subunits exhibit domain swaps and asymmetric strand exchanges that allow them to complete the two propellers and connect them. Thus, the modular and metamorphic nature of these subunits enabled dramatic changes in tertiary and quaternary structure, while maintaining the lectin function. These oligomers therefore comprise putative intermediates via which beta-propellers can evolve from smaller elements. Our data also suggest that the ability of one sequence to equilibrate between different structures can be evolutionary optimized, thus facilitating the emergence of new structures.