Authors: Muhammad Ali, Roshan Ali, Israr Ali Khan, Irshad Ahmad, Nighat Nawaz, Simon G. Patching
The trace metal zinc is essential in all types of organisms, where it has many catalytic, structural and regulatory functions. Zinc homeostasis in cells and organelles is maintained by various types of zinc transport protein. These include Cation Diffusion Facilitator (CDF) family proteins, which export zinc to the extracellular space or to the cytoplasm. Homologous CDF proteins are found in both prokaryotes and eukaryotes, where the human variants are the ZnTs or SLC30 family. One of the first and best characterised prokaryotic CDFs is the Escherichia coli zinc exporter ZitB, which is driven by the proton motive force in an antiport manner. In this article we provide an analytical review and expand on the biochemical and computational characterisation of ZitB and assess its potential for high-resolution three-dimensional structure determination. Consistent with structures determined for other CDF proteins (YiiP, ZnTs 3, 4, 7 and 8), the 313 residues of ZitB are predicted to form six transmembrane spanning α-helices with a long cytoplasmic C-terminal tail. An unusual feature of ZitB is an exceptionally high (8.0%) content of histidine residues. Using the IPTG-inducible plasmid pTTQ18, we demonstrate the cloning and amplified expression in E. coli of non-tagged, wild-type ZitB at levels of ~15% of total protein in preparations of inner membranes. ZitB was solubilised in the mild detergent n-dodecyl-β-D-maltoside (DDM) and purified by immobilised metal affinity chromatography in yields of ~1.8 mg per litre of culture medium. The structural integrity of purified ZitB was confirmed by mass spectrometry and circular dichroism spectroscopy.
Comments: 25 Pages.
Download: PDF
[v1] 2025-04-07 15:43:07
Unique-IP document downloads: 166 times
Vixra.org is a pre-print repository rather than a journal. Articles hosted may not yet have been verified by peer-review and should be treated as preliminary. In particular, anything that appears to include financial or legal advice or proposed medical treatments should be treated with due caution. Vixra.org will not be responsible for any consequences of actions that result from any form of use of any documents on this website.
Add your own feedback and questions here:
You are equally welcome to be positive or negative about any paper but please be polite. If you are being critical you must mention at least one specific error, otherwise your comment will be deleted as unhelpful.