The spatiotemporal regulation of chromosome segregation and cell division in Caulobacter crescentus is mediated by two different P-loop ATPases, ParA and MipZ. Both of these proteins form dynamic concentration gradients that control the positioning of regulatory targets within the cell. Their proper localization depends on their nucleotide-dependent cycling between a monomeric and a dimeric state and on the ability of the dimeric species to associate with the nucleoid. In this study, we use a combination of genetic screening, biochemical analysis and hydrogen/deuterium exchange mass spectrometry to comprehensively map the residues mediating the interactions of MipZ and ParA with DNA. We show that MipZ has non-specific DNA-binding activity that relies on an array of positively charged and hydrophobic residues lining both sides of the dimer interface. Extending our analysis to ParA, we find that the MipZ and ParA DNA-binding sites differ markedly in composition, although their relative positions on the dimer surface and their mode of DNA binding are conserved. In line with previous experimental work, bioinformatic analysis suggests that the same principles may apply to other members of the P-loop ATPase family. P-loop ATPases thus share common mechanistic features, although their functions have diverged considerably during the course of evolution.
The PEX1/PEX6 AAA-ATPase is required for the biogenesis and maintenance of peroxisomes. Mutations in and disrupt peroxisomal matrix protein import and are the leading cause of Peroxisome Biogenesis Disorders (PBDs). The most common disease-causing mutation in PEX1 is the PEX1 allele, which results in a reduction of peroxisomal protein import.
WD repeat domain 74 (WDR74) is a nucleolar protein involved in the early stages of pre-60S maturation in the ribosome biogenesis pathway. In later stages, WDR74 interacts with MTR4, an RNA helicase that functions with the exosome nuclease complex, and is dissociated upon ATP hydrolysis by the chaperone-like nuclear VCP-like 2 (NVL2) AAA-ATPase. We previously reported that ATP hydrolysis-defective NVL2 causes aberrant accumulation of WDR74 on the MTR4-exosome complex at the nucleolar periphery and in the nucleoplasm and that this nuclear redistribution of WDR74 leads to the unusual cleavage of the early rRNA precursor within the internal transcribed spacer 1 sequence.
ATPase family AAA domain-containing protein 2 (ATAD2) is significantly up-regulated in many cancer types and contributes to poor patient outcomes. ATAD2 exhibits a multidomain architecture comprising an N-terminal acidic domain, two AAA+ ATPase domains, a bromodomain, and a C-terminal domain. The AAA+ ATPase domain facilitates protein oligomerization and ATP binding, while the bromodomain recognizes acetylated lysine in histones and nonhistone proteins.
The histone chaperone FAcilitates Chromatin Transcription (FACT) is a heterodimeric complex consisting of Spt16 and Pob3, crucial for preserving nucleosome integrity during transcription and DNA replication. Loss of FACT leads to cryptic transcription and heterochromatin defects. FACT was shown to interact with Abo1, an AAA + family histone chaperone involved in nucleosome dynamics.
The ribosome maturation factor Rea1 (or Midasin) catalyses the removal of assembly factors from large ribosomal subunit precursors and promotes their export from the nucleus to the cytosol. Rea1 consists of nearly 5000 amino-acid residues and belongs to the AAA+ protein family. It consists of a ring of six AAA+ domains from which the ≈1700 amino-acid residue linker emerges that is subdivided into stem, middle and top domains.
