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

We have recently isolated SMAP (Smg GDS-associated protein; Smg GDS: small G protein GDP dissociation stimulator) as a novel Smg GDS-associated protein, which has Armadillo repeats and is phosphorylated by Src tyrosine kinase. SMAP is a human counterpart of mouse KAP3 (kinesin superfamily-associated protein) that is associated with mouse KIF3A/B (a kinesin superfamily protein), which functions as a microtubule-based ATPase motor for organelle transport. We isolated here a SMAP-interacting protein from a human brain cDNA library, identified it to be a human homolog of Xenopus XCAP-E (Xenopus chromosome-associated polypeptide), a subunit of condensins that regulate the assembly and structural maintenance of mitotic chromosomes, and named it HCAP (Human chromosome-associated polypeptide). Tissue and subcellular distribution analyses indicated that HCAP was ubiquitously expressed and highly concentrated in the nuclear fraction, where SMAP and KIF3B were also present. SMAP was extracted as a ternary complex with HCAP and KIF3B from the nuclear fraction in the presence of Mg-ATP. The results suggest that SMAP/KAP3 serves as a linker between HCAP and KIF3A/B in the nucleus, and that SMAP/KAP3 plays a role in the interaction of chromosomes with an ATPase motor protein.
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PMID:Complex formation of SMAP/KAP3, a KIF3A/B ATPase motor-associated protein, with a human chromosome-associated polypeptide. 950 51

RecN is a highly conserved, SMC-like protein in bacteria. It plays an important role in the repair of DNA double-strand breaks and is therefore a key factor in maintaining genome integrity. The insolubility of Escherichia coli RecN has limited efforts to unravel its function. We overcame this limitation by replacing the resident coding sequence with that of Haemophilus influenzae RecN. The heterologous construct expresses Haemophilus RecN from the SOS-inducible E. coli promoter. The hybrid gene is fully functional, promoting survival after I-SceI induced DNA breakage, gamma irradiation or exposure to mitomycin C as effectively as the native gene, indicating that the repair activity is conserved between these two species. H. influenzae RecN is quite soluble, even when expressed at high levels, and is readily purified. Its analysis by ionisation-mass spectrometry, gel filtration and glutaraldehyde crosslinking indicates that it is probably a dimer under physiological conditions, although a higher multimer cannot be excluded. The purified protein displays a weak ATPase activity that is essential for its DNA repair function in vivo. However, no DNA-binding activity was detected, which contrasts with RecN from Bacillus subtilis. RecN proteins from Aquifex aeolicus and Bacteriodes fragilis also proved soluble. Neither binds DNA, but the Aquifex RecN has weak ATPase activity. Our findings support studies indicating that RecN, and the SOS response in general, behave differently in E. coli and B. subtilis. The hybrid recN reported provides new opportunities to study the genetics and biochemistry of how RecN operates in E. coli.
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PMID:A soluble RecN homologue provides means for biochemical and genetic analysis of DNA double-strand break repair in Escherichia coli. 1984 53

Structural Maintenance of Chromosomes (SMC) family proteins participate in multisubunit complexes that govern chromosome structure and dynamics. SMC-containing condensin complexes create chromosome topologies essential for mitosis/meiosis, gene expression, recombination, and repair. Many eukaryotes have two condensin complexes (I and II); C. elegans has three (I, II, and the X-chromosome specialized condensin IDC) and their regulation is poorly understood. Here we identify a novel SMC-like protein, SMCL-1, that binds to C. elegans condensin SMC subunits, and modulates condensin functions. Consistent with a possible role as a negative regulator, loss of SMCL-1 partially rescued the lethal and sterile phenotypes of a hypomorphic condensin mutant, while over-expression of SMCL-1 caused lethality, chromosome mis-segregation, and disruption of condensin IDC localization on X chromosomes. Unlike canonical SMC proteins, SMCL-1 lacks hinge and coil domains, and its ATPase domain lacks conserved amino acids required for ATP hydrolysis, leading to the speculation that it may inhibit condensin ATPase activity. SMCL-1 homologs are apparent only in the subset of Caenorhabditis species in which the condensin I and II subunit SMC-4 duplicated to create the condensin IDC- specific subunit DPY-27, suggesting that SMCL-1 helps this lineage cope with the regulatory challenges imposed by evolution of a third condensin complex. Our findings uncover a new regulator of condensins and highlight how the duplication and divergence of SMC complex components in various lineages has created new proteins with diverse functions in chromosome dynamics.
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PMID:An SMC-like protein binds and regulates Caenorhabditis elegans condensins. 2830 65

The structural maintenance of chromosomes (SMC) proteins play a vital role in genome stability and chromosome organization in all domains of life. Previous reports show that smc deletion causes decondensation of chromosome and an increased frequency of anucleated cells in bacteria. However, smc deletion in both Mycobacterium smegmatis and Mycobacterium tuberculosis did not affect chromosome condensation or the frequency of anucleated cells. In an attempt to understand this difference in M. smegmatis, we investigated the function of MksB (MsMksB), an alternate SMC-like protein. Like other bacterial SMCs, MsMksB is also an elongated homodimer, in which a central hinge domain connects two globular ATPase head domains via two coiled-coil arms. We show that full-length MsMksB binds to different topological forms of DNA without any preferences. However, the hinge and headless domains prefer binding to single-stranded DNA (ssDNA) and linear double-stranded DNA (dsDNA), respectively. The binding of MsMksB to DNA was independent of ATP as its ATP hydrolysis deficient mutant was also proficient in DNA binding. Further, the cytological profiling studies revealed that only the full-length MsMksB and none of its structural domains could condense the bacterial chromosome. This observation indicates the plausibility of the concerted action of different structural domains of SMC to bind and condense the chromosome. Moreover, MsMksB exhibited DNA stimulated ATPase activity, in addition to its intrinsic ATPase activity. Taken together, we have elucidated the function of an alternate bacterial condensin protein MksB and its structural domains in DNA binding and condensation.
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PMID:MksB, an alternate condensin from Mycobacterium smegmatis is involved in DNA binding and condensation. 3214 49