Biology subjects

Kozlov, G.

Publications and source records attributed to Kozlov, G..

4 recordsLinked to original sources

bioRxiv2021

Structural basis for feedforward control in the PINK1/parkin pathway

PINK1 and parkin constitute a mitochondrial quality control system mutated in Parkinsons disease. PINK1, a kinase, phosphorylates ubiquitin to recruit parkin, an E3 ubiquitin ligase, to mitochondria. PINK1 controls both parkin localization and activity through phosphorylation of both ubiquitin and the ubiquitin-like (Ubl) domain of parkin. Here, we observe that phospho-ubiquitin can bind to two distinct sites on parkin, a high affinity site on RING1 that controls parkin localization, and a low affinity site on RING0 that releases parkin autoinhibition. Surprisingly, NMR titrations and ubiquitin vinyl sulfone assays show that the RING0 site has higher affinity for phospho-ubiquitin than the phosphorylated Ubl. Parkin could be activated by micromolar concentrations of tetra-phospho-ubiquitin chains that mimic a mitochondrion bearing multiple phosphorylated ubiquitins. A chimeric form of parkin with the Ubl domain replaced by ubiquitin was readily activated by PINK1 phosphorylation. In all cases, mutation of the binding site on RING0 abolished parkin activation. The feedforward mechanism of parkin activation confers robustness and rapidity to the PINK1-parkin pathway and likely represents an intermediate step in its evolutionary development.

biochemistry↗

bioRxiv2021

Crystal structure of a bacterial CNNM magnesium transporter

CBS-pair domain divalent metal cation transport mediators (CNNMs) are a broadly conserved family of integral membrane proteins with close to 90,000 protein sequences known. CNNM proteins are associated with Mg2+ transport but it is not known if they mediate transport themselves or regulate other transporters. Here, we determined the crystal structure of an archaeal CNNM protein with Mg2+-ATP bound. The structure reveals a novel transmembrane fold for the DUF21 domain, the largest family of domains of unknown function. The protein has a negatively charged cavity that penetrates halfway through the membrane suggesting it functions as a cation transporter. The cytosolic portion of the protein is comprised of highly charged four-helix bundle and a CBS-pair domain. HDX-MS experiments, molecular dynamics, and additional crystal structures show that the cytosolic domains undergo large conformational changes upon nucleotide binding suggesting a mechanism of regulation shared between human and bacterial orthologs. The molecular characterization of CNNM proteins has profound implications for understanding their biological functions in human diseases, including cancer, and in animals, bacteria and plants.

biophysics↗

bioRxiv2021

Poly(A) binding protein is required for mRNP remodeling to form P-bodies in mammalian cells

Compartmentalization of mRNA through formation of RNA granules is involved in many cellular processes, yet it is not well understood. mRNP complexes undergo dramatic changes in protein compositions, reflected by markers of P-bodies and stress granules. Here, we show that PABPC1, albeit absent in P-bodies, plays important role in P-body formation. Depletion of PABPC1 decreases P-body population in unstressed cells. Upon stress in PABPC1 depleted cells, individual P-bodies fail to form and instead P-body proteins assemble on PABPC1-containing stress granules. We hypothesize that mRNP recruit proteins via PABPC1 to assemble P-bodies, before PABPC1 is displaced from mRNP. Further, we demonstrate that GW182 can mediate P-body assembly. These findings help us understand the early stages of mRNP remodeling and P-body formation. Summary statementA novel role of poly(A) binding protein is reported in P-body formation

biochemistry↗

bioRxiv2021

Paip2 associates with PABPC1 on mRNA, and may facilitate PABPC1 dissociation from mRNA upon deadenylation

Poly(A) binding protein cytoplasmic 1 (PABPC1) is an essential translational initiation factor. PABPC1 recognizes proteins through conserved PABPC1-interacting motifs 1 and 2 (PAM1 and PAM2). PABPC1-interacting protein-2 (Paip2) interacts with PABPC1 and modulates its activities. Here, we report that the formation of Paip2/PABPC1 complex protects it from proteasome independent degradation. We also show that PAM2 is critical for Paip2/PABPC1 interaction in vivo, in agreement with the observation that Paip2 requires PAM2 to interact with PABPC1 on mRNA. Lastly, we propose a role for Paip2 in displacing PABPC1 at the final stage of mRNA deadenylation when the poly(A) tail is partly degraded.

biochemistry↗