Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.6.1.3 (ATPase)
 65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Overexpressed PIF1 DNA helicase was purified from mitochondria to near homogeneity. Its ATPase and unwinding properties were characterized. The enzyme specifically utilizes ATP (or dATP) and MgCl2 (and to a lesser extent MnCl2). ATPase activity requires single-stranded DNA as an effector, duplex DNA being 100-fold less effective. The Keff, defined as the concentration of DNA required to achieve half-maximal ATPase activity, does not depend on single-stranded DNA length. Long duplex DNAs are poorly unwound and, moreover, dilution of the enzyme and its DNA substrate in the assay decreases DNA helicase activity. These data indicate that PIF1 helicase is a distributive enzyme, frequently turning from one DNA molecule to another. When forked substrates are used, unwinding by PIF1 is markedly stimulated. The enzyme has a sedimentation coefficient of 6.5 S, suggesting that it exists as a monomer in solution.
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PMID:PIF1 DNA helicase from Saccharomyces cerevisiae. Biochemical characterization of the enzyme. 825 34

The evolutionary conserved PIF1 DNA helicase family appears to have largely nonoverlapping cellular functions. To better understand the functions of human PIF1, we investigated biochemical properties of this protein. Analysis of single-stranded (ss) DNA-dependent ATPase activity revealed nonstructural ssDNA to greatly stimulate ATPase activity due to a high affinity for PIF1, even though PIF1 preferentially unwinds forked substrates. This suggests that PIF1 needs a ssDNA region for loading and a forked structure for translocation entrance into a double strand region. Deletion analysis demonstrated novel functions of a unique N-terminal portion, named the PIF1 N-terminal (PINT) domain. When the PINT domain was truncated, apparent affinity for ssDNA and unwinding activity were much reduced, even though the maximum velocity of ATPase activity and K(m) value for ATP were not affected. We suggest that the PINT domain contributes to enhancing the interaction with ssDNA through intrinsic binding activity. In addition, we found DNA strand-annealing activity, also residing in the PINT domain. Notably, the unwinding and annealing activities were inhibited by replication protein A. These results suggest that the functions of PIF1 might be restricted with particular situations and DNA structures.
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PMID:Biochemical analysis of human PIF1 helicase and functions of its N-terminal domain. 1883 53