The Proline Rich Homeodomain Protein PRH/Hhex Forms Stable Oligomers That Are Highly Resistant to Denaturation

Abstract

BackgroundMany transcription factors control gene expression by binding to specific DNA sequences at or near the genes that they regulate. However, some transcription factors play more global roles in the control of gene expression by altering the architecture of sections of chromatin or even the whole genome. The ability to form oligomeric protein assemblies allows many of these proteins to manipulate extensive segments of DNA or chromatin via the formation of structures such as DNA loops or protein-DNA fibres.Principal FindingsHere we show that the proline rich homeodomain protein PRH/Hhex forms predominantly octameric and/or hexadecameric species in solution as well as larger assemblies. We show that these assemblies are highly stable resisting denaturation by temperature and chemical denaturants.ConclusionThese data indicate that PRH is functionally and structurally related to the Lrp/AsnC family of proteins, a group of proteins that are known to act globally to control gene expression in bacteria and archaea.

Misregulation of the proline rich homeodomain (PRH/HHEX) protein in cancer cells and its consequences for tumour growth and invasion

“…The PRH protein has a predicted molecular mass of 30 kDa, but in vivo and in vitro PRH forms homo-oligomeric complexes that appear to be octameric and hexadecameric [ 23 – 25 ]. These complexes are highly stable in vitro resisting denaturation by temperature and chemical agents [ 26 ]. The PRH monomer has three functional domains: a 136 amino acid N-terminal glycine-, alanine- and proline-rich domain, a central 60 amino acid proline-rich homeodomain, and a 73 amino acid acidic C-terminal domain (Fig.…”

Evidence for a Role of the Polysaccharide Capsule Transport Proteins in Pertussis Pathogenesis

“…It is to be noted that despite the presence of guanidine hydrocholoride during the purification process, we were still able to observe high MW BvgS complexes. However, large hydrophobic proteins, in particular membrane proteins or proteins that contain proline rich homeodomains have been reported to be resistant to denaturation by urea or guanidine hydrochloride [60] – [62] . It has been suggested that in eukaryotic system, proline rich regions mediate protein dimerization and oligomerization [62] , [63] .…”

“…However, large hydrophobic proteins, in particular membrane proteins or proteins that contain proline rich homeodomains have been reported to be resistant to denaturation by urea or guanidine hydrochloride [60] – [62] . It has been suggested that in eukaryotic system, proline rich regions mediate protein dimerization and oligomerization [62] , [63] . BvgS sensor contains two separate alanine-proline rich regions within the cytoplasmic histidine kinase and receiver domains [12] , [64] .…”