PDBsum entry 4lms

Photosynthesis

PDB id: 4lms

Contents

Protein chains

80 a.a.

162 a.a.

68 a.a.

Ligands

M1V ×2

DBV ×2

CYC ×4

P6G ×2

Waters ×764

PDB id:

4lms

Name:

Photosynthesis

Title:

Light harvesting complex pc645 from the cryptophyte chroomonas sp. Ccmp270

Structure:

Cryptophyte phycocyanin (alpha-1 chain). Chain: a. Cryptophyte phycocyanin (beta chain). Chain: b, d. Cryptophyte phycocyanin (alpha-2 chain). Chain: c

Source:

Chroomonas sp.. Organism_taxid: 3029. Strain: ccmp270. Strain: ccmp270

Resolution:

1.35Å R-factor: 0.145 R-free: 0.181

Authors:

S.J.Harrop,K.E.Wilk,P.M.G.Curmi

Key ref:

S.J.Harrop et al. (2014). Single-residue insertion switches the quaternary structure and exciton states of cryptophyte light-harvesting proteins. Proc Natl Acad Sci U S A, 111, E2666. PubMed id: 24979784 DOI: 10.1073/pnas.1402538111

Date:

11-Jul-13 Release date: 18-Jun-14

Protein chain

U5T880  (PHEA1_CHRS2) -  Phycocyanin PC645 alpha-1 subunit from Chroomonas sp. (strain CCMP270)

Seq: 132 a.a.

Struc: 80 a.a.

Protein chains

U5T8F2  (PHEB_CHRS2) -  Phycocyanin PC645 beta subunit from Chroomonas sp. (strain CCMP270)

Seq: 177 a.a.

Struc: 162 a.a.*

Protein chain

U5T8W5  (PHEA2_CHRS2) -  Phycocyanin PC645 alpha-2 subunit from Chroomonas sp. (strain CCMP270)

Seq: 122 a.a.

Struc: 68 a.a.*

* PDB and UniProt seqs differ at 3 residue positions (black crosses)

DOI no: 10.1073/pnas.1402538111

Proc Natl Acad Sci U S A 111:E2666 (2014)

PubMed id: 24979784

Single-residue insertion switches the quaternary structure and exciton states of cryptophyte light-harvesting proteins.

S.J.Harrop, K.E.Wilk, R.Dinshaw, E.Collini, T.Mirkovic, C.Y.Teng, D.G.Oblinsky, B.R.Green, K.Hoef-Emden, R.G.Hiller, G.D.Scholes, P.M.Curmi.

ABSTRACT

Observation of coherent oscillations in the 2D electronic spectra (2D ES) of photosynthetic proteins has led researchers to ask whether nontrivial quantum phenomena are biologically significant. Coherent oscillations have been reported for the soluble light-harvesting phycobiliprotein (PBP) antenna isolated from cryptophyte algae. To probe the link between spectral properties and protein structure, we determined crystal structures of three PBP light-harvesting complexes isolated from different species. Each PBP is a dimer of αβ subunits in which the structure of the αβ monomer is conserved. However, we discovered two dramatically distinct quaternary conformations, one of which is specific to the genus Hemiselmis. Because of steric effects emerging from the insertion of a single amino acid, the two αβ monomers are rotated by ∼73° to an "open" configuration in contrast to the "closed" configuration of other cryptophyte PBPs. This structural change is significant for the light-harvesting function because it disrupts the strong excitonic coupling between two central chromophores in the closed form. The 2D ES show marked cross-peak oscillations assigned to electronic and vibrational coherences in the closed-form PC645. However, such features appear to be reduced, or perhaps absent, in the open structures. Thus cryptophytes have evolved a structural switch controlled by an amino acid insertion to modulate excitonic interactions and therefore the mechanisms used for light harvesting.