Abstracts » Zoology and wildlife conservation

New break for archaeal enzyme

Article Abstract:

A study of an unusual topoisomerase from the archaeon Sulfolobus shibatae has led to the discovery of a new subfamily of type II DNA topoisomerases named S. shibatae DNA topoisomerase VI. This type II DNA topoisomerase is ATP-dependent and exhibits the topological signature of all enzymes of its type as it eliminates supercoils two at a time. Minimal sequence homology between the two subunits of the S. shibatae enzyme and polypeptides of the known type II topoisomerases was observed. This new DNA topoisomerase with a distinct primary structure may explain the absence of at least one type II DNA topoisomerase in the Methanococcus jannaschii, which is required for viability.

Enzymes, Identification and classification

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Structure and mechanism of DNA topoisomerase II

Article Abstract:

Type II deoxyribonucleic acid (DNA) topoisomerases are cellular enzymes that serve to separate newly replicated chromosome pairs, aside from being vital in chromosome condensation and in altering DNA superhelicity. The structure of yeast type II DNA topoisomerase shows a heart-shaped dimeric protein with a large hole in the middle. Its molecular model shows a clamp with jaws at both ends that are linked by multiple joints. Type II topoisomerases make cleavages and an opening in one DNA duplex, through which a second duplex is then passed, before resealing the break.

Analysis

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Study of allosteric communication between protomers by immunotagging

Article Abstract:

ATP binding to a single protomer of type II DNA topoisomerase can induce an allosteric change throughout the enzyme. A topoisomerase with a subunit defective in ATP binding which was immunotagged and one wild-type subunit were used to demonstrate that binding at a single subunit can have conformational effects in all subunits. The techniques used should prove useful in the study of allosteric communication among components of multimeric complexes.

Proteins, Allosteric proteins, Protein conformation

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