Biomedical subjects

Michael J Eddins

Publications and source records attributed to Michael J Eddins.

3 recordsLinked to original sources

PubMed2006

Mms2-Ubc13 covalently bound to ubiquitin reveals the structural basis of linkage-specific polyubiquitin chain formation.

Lys63-linked polyubiquitin chains participate in nonproteolytic signaling pathways, including regulation of DNA damage tolerance and NF-kappaB activation. E2 enzymes bound to ubiquitin E2 variants (UEV) are vital in these pathways, synthesizing Lys63-linked polyubiquitin chains, but how these complexes achieve specificity for a particular lysine linkage has been unclear. We have determined the crystal structure of an Mms2-Ubc13-ubiquitin (UEV-E2-Ub) covalent intermediate with donor ubiquitin linked to the active site residue of Ubc13. In the structure, the unexpected binding of a donor ubiquitin of one Mms2-Ubc13-Ub complex to the acceptor-binding site of Mms2-Ubc13 in an adjacent complex allows us to visualize at atomic resolution the molecular determinants of acceptor-ubiquitin binding. The structure reveals the key role of Mms2 in allowing selective insertion of Lys63 into the Ubc13 active site and suggests a molecular model for polyubiquitin chain elongation.

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PubMed2004

Ubiquitin: structures, functions, mechanisms.

Ubiquitin is the founding member of a family of structurally conserved proteins that regulate a host of processes in eukaryotic cells. Ubiquitin and its relatives carry out their functions through covalent attachment to other cellular proteins, thereby changing the stability, localization, or activity of the target protein. This article reviews the basic biochemistry of these protein conjugation reactions, focusing on ubiquitin itself and emphasizing recent insights into mechanism and specificity.

Animals↗

PubMed2002

Crystallization and low-resolution structure of an effector-caspase/P35 complex: similarities and differences to an initiator-caspase/P35 complex.

The aspartate-specific caspases play a pivotal role in the execution of programmed cell death and therefore constitute important targets for the control of apoptosis. Upon ectopic expression, baculovirus P35 inhibits apoptosis in phylogenetically diverse organisms by suppressing the proteolytic activity of the cellular caspases in a cleavage-dependent mechanism. After cleavage by caspase, the P35 fragments remain bound to the target caspase, forming an inhibitory complex that sequesters the caspase from further activity. Crystals of a complex between P35 and Sf-caspase-1, an insect effector-caspase, were grown. A 5.2 A resolution structure of this inhibitory complex was determined by molecular-replacement methods. The structure reveals few regions of interaction between the two proteins, much like that observed in the structure of the recently solved human initiator-caspase/P35 complex. In the effector-caspase/P35 complex structure presented here, the P35 molecule shifts towards a loop that is conserved in effector caspases but absent in initiator caspase. This shift could strengthen interactions between the two proteins and may explain the preference of P35 for inhibiting effector-caspases.

Animals↗