6ALI

Solution NMR structure of a putative thioredoxin (ECH_0218) in the oxidized state from Ehrlichia chaffeensis, the etiological agent responsible for human monocytic ehrlichiosis. Seattle Structural Genomics Center for Infectious Disease target EhchA.00546.a

Replaces:  2MOD

Summary for 6ALI

• Entry DOI: 10.2210/pdb6ali/pdb
• NMR Information: BMRB: 19938
• Descriptor: Thioredoxin (1 entity in total)
• Functional Keywords: ssgcid, infectious diseases, thioredoxin, human monocytic ehrlichiosis, tick diseases, oxidoreductase, structural genomics, seattle structural genomics center for infectious disease
• Biological source: Ehrlichia chaffeensis (strain ATCC CRL-10679 / Arkansas)
• Total number of polymer chains: 1
• Total formula weight: 14362.21

Authors

Buchko, G.W.,Seattle Structural Genomics Center for Infectious Disease (SSGCID) (deposition date: 2017-08-08, release date: 2017-09-06, Last modification date: 2024-10-09)

Primary citation

Buchko, G.W.,Hewitt, S.N.,Van Voorhis, W.C.,Myler, P.J.
Solution NMR structures of oxidized and reduced Ehrlichia chaffeensis thioredoxin: NMR-invisible structure owing to backbone dynamics.
Acta Crystallogr F Struct Biol Commun, 74:46-56, 2018

PubMed Abstract: Thioredoxins are small ubiquitous proteins that participate in a diverse variety of redox reactions via the reversible oxidation of two cysteine thiol groups in a structurally conserved active site. Here, the NMR solution structures of a reduced and oxidized thioredoxin from Ehrlichia chaffeensis (Ec-Trx, ECH_0218), the etiological agent responsible for human monocytic ehrlichiosis, are described. The overall topology of the calculated structures is similar in both redox states and is similar to those of other thioredoxins: a five-stranded, mixed β-sheet (β1-β3-β2-β4-β5) surrounded by four α-helices. Unlike other thioredoxins studied by NMR in both redox states, the H-N HSQC spectrum of reduced Ec-Trx was missing eight additional amide cross peaks relative to the spectrum of oxidized Ec-Trx. These missing amides correspond to residues Cys35-Glu39 in the active-site-containing helix (α2) and Ser72-Ile75 in a loop near the active site, and suggest a change in backbone dynamics on the millisecond-to-microsecond timescale associated with the breakage of an intramolecular Cys32-Cys35 disulfide bond in a thioredoxin. A consequence of the missing amide resonances is the absence of observable or unambiguous NOEs to provide the distance restraints necessary to define the N-terminal end of the α-helix containing the CPGC active site in the reduced state. This region adopts a well defined α-helical structure in other reported reduced thioredoxin structures, is mostly helical in oxidized Ec-Trx and CD studies of Ec-Trx in both redox states suggests there is no significant difference in the secondary structure of the protein. The NMR solution structure of reduced Ec-Trx illustrates that the absence of canonical structure in a region of a protein may be owing to unfavorable dynamics prohibiting NOE observations or unambiguous NOE assignments.

PubMed: 29372907
DOI: 10.1107/S2053230X1701799X

Experimental method

SOLUTION NMR