PDBsum entry 2kac

Immune system

PDB id: 2kac

Contents

Protein chain

64 a.a. *

* Residue conservation analysis

PDB id:

2kac

Name:

Immune system

Title:

Nmr solution structure of kx6e protl mutant

Structure:

Protein l. Chain: a. Fragment: residues in database 111-173. Engineered: yes. Mutation: yes

Source:

Peptostreptococcus magnus. Organism_taxid: 1260. Expressed in: escherichia coli. Expression_system_taxid: 562.

NMR struc:

20 models

Authors:

B.Lopez-Mendez,X.Tadeo,M.Pons,O.Millet

Key ref:

X.Tadeo et al. (2009). Structural basis for the aminoacid composition of proteins from halophilic archea. Plos Biol, 7, e1000257. PubMed id: 20016684

Date:

04-Nov-08 Release date: 20-Oct-09

Protein chain

Q51912  (Q51912_FINMA) -  Gram-positive cocci surface proteins LPxTG domain-containing protein from Finegoldia magna

Seq: 719 a.a.

Struc: 64 a.a.*

* PDB and UniProt seqs differ at 8 residue positions (black crosses)

Enzyme reactions

• Enzyme class: E.C.?

Plos Biol 7:e1000257 (2009)

PubMed id: 20016684

Structural basis for the aminoacid composition of proteins from halophilic archea.

X.Tadeo, B.López-Méndez, T.Trigueros, A.Laín, D.Castaño, O.Millet.

ABSTRACT

Proteins from halophilic organisms, which live in extreme saline conditions, have evolved to remain folded at very high ionic strengths. The surfaces of halophilic proteins show a biased amino acid composition with a high prevalence of aspartic and glutamic acids, a low frequency of lysine, and a high occurrence of amino acids with a low hydrophobic character. Using extensive mutational studies on the protein surfaces, we show that it is possible to decrease the salt dependence of a typical halophilic protein to the level of a mesophilic form and engineer a protein from a mesophilic organism into an obligate halophilic form. NMR studies demonstrate complete preservation of the three-dimensional structure of extreme mutants and confirm that salt dependency is conferred exclusively by surface residues. In spite of the statistically established fact that most halophilic proteins are strongly acidic, analysis of a very large number of mutants showed that the effect of salt on protein stability is largely independent of the total protein charge. Conversely, we quantitatively demonstrate that halophilicity is directly related to a decrease in the accessible surface area.