Assuntos
Proteínas AAA/química , Proteínas AAA/genética , Proteínas AAA/metabolismo , Adenosina Trifosfatases/metabolismo , Trifosfato de Adenosina/metabolismo , Microscopia Crioeletrônica , Cristalografia por Raios X , Desenvolvimento de Medicamentos , Humanos , Simulação de Dinâmica Molecular , Mutação , Conformação ProteicaRESUMO
Bacterial enhancer-binding proteins (bEBPs) are specialised transcriptional activators. bEBPs are hexameric AAA+ ATPases and use ATPase activities to remodel RNA polymerase (RNAP) complexes that contain the major variant sigma factor, σ54 to convert the initial closed complex to the transcription competent open complex. Earlier crystal structures of AAA+ domains alone have led to proposals of how nucleotide-bound states are sensed and propagated to substrate interactions. Recently, the structure of the AAA+ domain of a bEBP bound to RNAP-σ54-promoter DNA was revealed. Together with structures of the closed complex, an intermediate state where DNA is partially loaded into the RNAP cleft and the open promoter complex, a mechanistic understanding of how bEBPs use ATP to activate transcription can now be proposed. This review summarises current structural models and the emerging understanding of how this special class of AAA+ proteins utilises ATPase activities to allow σ54-dependent transcription initiation.
Assuntos
Proteínas AAA/metabolismo , Bactérias/genética , Proteínas de Bactérias/metabolismo , Regulação Bacteriana da Expressão Gênica , Fatores de Transcrição/metabolismo , Ativação Transcricional , Proteínas AAA/química , Proteínas AAA/genética , Trifosfato de Adenosina/metabolismo , Bactérias/química , Bactérias/metabolismo , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , Modelos Moleculares , Conformação Proteica , Multimerização Proteica , RNA Polimerase Sigma 54/química , RNA Polimerase Sigma 54/genética , RNA Polimerase Sigma 54/metabolismo , Fatores de Transcrição/química , Fatores de Transcrição/genéticaRESUMO
ATPases associated with diverse cellular activities (AAA+ proteins) are macromolecular machines that convert the chemical energy contained in ATP molecules into powerful mechanical forces to remodel a vast array of cellular substrates, including protein aggregates, macromolecular complexes and polymers. AAA+ proteins have key functionalities encompassing unfolding and disassembly of such substrates in different subcellular localizations and, hence, power a plethora of fundamental cellular processes, including protein quality control, cytoskeleton remodelling and membrane dynamics. Over the past 35 years, many of the key elements required for AAA+ activity have been identified through genetic, biochemical and structural analyses. However, how ATP powers substrate remodelling and whether a shared mechanism underlies the functional diversity of the AAA+ superfamily were uncertain. Advances in cryo-electron microscopy have enabled high-resolution structure determination of AAA+ proteins trapped in the act of processing substrates, revealing a conserved core mechanism of action. It has also become apparent that this common mechanistic principle is structurally adjusted to carry out a diverse array of biological functions. Here, we review how substrate-bound structures of AAA+ proteins have expanded our understanding of ATP-driven protein remodelling.
Assuntos
Proteínas AAA/química , Proteínas AAA/metabolismo , Adenosina Trifosfatases/química , Adenosina Trifosfatases/metabolismo , Trifosfato de Adenosina/metabolismo , Animais , Microscopia Crioeletrônica , Humanos , Hidrólise , Modelos Moleculares , Conformação ProteicaRESUMO
The AAA proteins are a family of enzymes that play key roles in diverse dynamic cellular processes, ranging from proteostasis to directional intracellular transport. Dysregulation of AAA proteins has been linked to several diseases, including cancer, suggesting a possible therapeutic role for inhibitors of these enzymes. In the past decade, new chemical probes have been developed for AAA proteins including p97, dynein, midasin, and ClpC1. In this review, we discuss how these compounds have been used to study the cellular functions and conformational dynamics of AAA proteins. We discuss future directions for inhibitor development and early efforts to utilize AAA protein inhibitors in the clinical setting.
Assuntos
Proteínas AAA/química , Proteínas AAA/fisiologia , Sondas Moleculares , Preparações Farmacêuticas , Proteínas AAA/metabolismo , Humanos , Organelas/metabolismo , Conformação ProteicaRESUMO
The innate immune sensor retinoic acid-inducible gene I (RIG-I) detects cytosolic viral RNA and requires a conformational change caused by both ATP and RNA binding to induce an active signaling state and to trigger an immune response. Previously, we showed that ATP hydrolysis removes RIG-I from lower-affinity self-RNAs (