PDBsum entry 5onc

Biosynthetic protein

PDB id: 5onc

Contents

Protein chains

366 a.a.

Metals

_CL ×5

Waters ×213

PDB id:

5onc

Name:

Biosynthetic protein

Title:

Catabolism of the cholesterol side chain in mycobacterium tuberculosis is controlled by a redox-sensitive thiol switch

Structure:

Steroid 3-ketoacyl-coa thiolase. Chain: a, b. Synonym: acetyl-coa acetyltransferase fada5,beta-ketoacyl-coa thiolase. Engineered: yes

Source:

Mycobacterium tuberculosis (strain atcc 25618 / h37rv). Organism_taxid: 83332. Gene: fada5, lh57_19345, rv3546. Expressed in: mycobacterium smegmatis. Expression_system_taxid: 1772.

Resolution:

2.19Å R-factor: 0.184 R-free: 0.226

Authors:

C.Schaefer,J.Kuper,N.S.Sampson,C.Kisker

Key ref:

R.Lu et al. (2017). Catabolism of the Cholesterol Side Chain in Mycobacterium tuberculosis Is Controlled by a Redox-Sensitive Thiol Switch. ACS Infect Dis, 3, 666-675. PubMed id: 28786661

Date:

03-Aug-17 Release date: 23-Aug-17

Protein chains

I6XHI4  (FADA5_MYCTU) -  Steroid 3-ketoacyl-CoA thiolase from Mycobacterium tuberculosis (strain ATCC 25618 / H37Rv)

Seq: 391 a.a.

Struc: 366 a.a.

Enzyme reactions

• Enzyme class: E.C.2.3.1.16 - acetyl-CoA C-acyltransferase.
• Reaction: an acyl-CoA + acetyl-CoA = a 3-oxoacyl-CoA + CoA

Molecule diagrams generated from .mol files obtained from the KEGG ftp site

reference

ACS Infect Dis 3:666-675 (2017)

PubMed id: 28786661

Catabolism of the Cholesterol Side Chain in Mycobacterium tuberculosis Is Controlled by a Redox-Sensitive Thiol Switch.

R.Lu, C.M.Schaefer, N.M.Nesbitt, J.Kuper, C.Kisker, N.S.Sampson.

ABSTRACT

Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis (TB), is a highly successful human pathogen and has infected approximately one-third of the world's population. Multiple drug resistant (MDR) and extensively drug resistant (XDR) TB strains and coinfection with HIV have increased the challenges of successfully treating this disease pandemic. The metabolism of host cholesterol by Mtb is an important factor for both its virulence and pathogenesis. In Mtb, the cholesterol side chain is degraded through multiple cycles of β-oxidation and FadA5 (Rv3546) catalyzes side chain thiolysis in the first two cycles. Moreover, FadA5 is important during the chronic stage of infection in a mouse model of Mtb infection. Here, we report the redox control of FadA5 catalytic activity that results from reversible disulfide bond formation between Cys59-Cys91 and Cys93-Cys377. Cys93 is the thiolytic nucleophile, and Cys377 is the general acid catalyst for cleavage of the β-keto-acyl-CoA substrate. The disulfide bond formed between the two catalytic residues Cys93 and Cys377 blocks catalysis. The formation of the disulfide bonds is accompanied by a large domain swap at the FadA5 dimer interface that serves to bring Cys93 and Cys377 in close proximity for disulfide bond formation. The catalytic activity of FadA5 has a midpoint potential of -220 mV, which is close to the Mtb mycothiol potential in the activated macrophage. The redox profile of FadA5 suggests that FadA5 is fully active when Mtb resides in the unactivated macrophage to maximize flux into cholesterol catabolism. Upon activation of the macrophage, the oxidative shift in the mycothiol potential will decrease the thiolytic activity by 50%. Thus, the FadA5 midpoint potential is poised to rapidly restrict cholesterol side chain degradation in response to oxidative stress from the host macrophage environment.