Biomedical subjects

James Yates

Publications and source records attributed to James Yates.

6 recordsLinked to original sources

PubMed2006

Double-stranded DNA translocation: structure and mechanism of hexameric FtsK.

FtsK is a DNA translocase that coordinates chromosome segregation and cell division in bacteria. In addition to its role as activator of XerCD site-specific recombination, FtsK can translocate double-stranded DNA (dsDNA) rapidly and directionally and reverse direction. We present crystal structures of the FtsK motor domain monomer, showing that it has a RecA-like core, the FtsK hexamer, and also showing that it is a ring with a large central annulus and a dodecamer consisting of two hexamers, head to head. Electron microscopy (EM) demonstrates the DNA-dependent existence of hexamers in solution and shows that duplex DNA passes through the middle of each ring. Comparison of FtsK monomer structures from two different crystal forms highlights a conformational change that we propose is the structural basis for a rotary inchworm mechanism of DNA translocation.

Adenosine Triphosphate↗

PubMed2006

Dissection of a functional interaction between the DNA translocase, FtsK, and the XerD recombinase.

Successful bacterial circular chromosome segregation requires that any dimeric chromosomes, which arise by crossing over during homologous recombination, are converted to monomers. Resolution of dimers to monomers requires the action of the XerCD site-specific recombinase at dif in the chromosome replication terminus region. This reaction requires the DNA translocase, FtsK(C), which activates dimer resolution by catalysing an ATP hydrolysis-dependent switch in the catalytic state of the nucleoprotein recombination complex. We show that a 62-amino-acid fragment of FtsK(C) interacts directly with the XerD C-terminus in order to stimulate the cleavage by XerD of BSN, a dif-DNA suicide substrate containing a nick in the 'bottom' strand. The resulting recombinase-DNA covalent complex can undergo strand exchange with intact duplex dif in the absence of ATP. FtsK(C)-mediated stimulation of BSN cleavage by XerD requires synaptic complex formation. Mutational impairment of the XerD-FtsK(C) interaction leads to reduction in the in vitro stimulation of BSN cleavage by XerD and a concomitant deficiency in the resolution of chromosomal dimers at dif in vivo, although other XerD functions are not affected.

Amino Acid Sequence↗

PubMed2004

Recombination and chromosome segregation.

The duplication of DNA and faithful segregation of newly replicated chromosomes at cell division is frequently dependent on recombinational processes. The rebuilding of broken or stalled replication forks is universally dependent on homologous recombination proteins. In bacteria with circular chromosomes, crossing over by homologous recombination can generate dimeric chromosomes, which cannot be segregated to daughter cells unless they are converted to monomers before cell division by the conserved Xer site-specific recombination system. Dimer resolution also requires FtsK, a division septum-located protein, which coordinates chromosome segregation with cell division, and uses the energy of ATP hydrolysis to activate the dimer resolution reaction. FtsK can also translocate DNA, facilitate synapsis of sister chromosomes and minimize entanglement and catenation of newly replicated sister chromosomes. The visualization of the replication/recombination-associated proteins, RecQ and RarA, and specific genes within living Escherichia coli cells, reveals further aspects of the processes that link replication with recombination, chromosome segregation and cell division, and provides new insight into how these may be coordinated.

Adenosine Triphosphatases↗

PubMed2004

Analysis of outpatient surgery center safety using an internet-based quality improvement and peer review program.

Assessing the quality of care delivered in office-based outpatient surgery centers is difficult because formerly there was no central data collection system. The American Association for Accreditation of Ambulatory Surgery Facilities (AAAASF), in its ongoing effort to assess and improve patient care, has developed an Internet-based quality improvement and peer review program to analyze outcomes for surgery centers it accredits. Reporting is mandatory for all surgeons operating in AAAASF-accredited facilities. Each surgeon must report all unanticipated sequelae and at least six random cases reviewed by an accepted peer review group biannually. A total of 411,670 procedures were analyzed during a 2-year period (from 2001 to 2002). There were 2597 sequelae reported during this period. The most common sequela was hematoma formation following breast augmentation. Infection occurred in 388 cases. Deep vein thrombosis, pulmonary embolism, and intraoperative cardiac arrhythmias were found to occur in a frequency consistent with previous reports. Significant complications (hematoma, hypertensive episode, wound infection, sepsis, and hypotension) were infrequent. A total of 1378 significant sequelae were reported for 411,670 procedures. This calculates to one unanticipated sequela in 299 procedures (an incidence of 0.33 percent). Seven deaths were reported. A death occurred in one in 58,810 procedures (0.0017 percent). The overall risk of death was comparable whether the procedure was performed in an AAAASF-accredited office surgery facility or a hospital surgery facility. This study documents an excellent safety record for surgical procedures performed in accredited office surgery facilities by board-certified surgeons.

Accreditation↗

PubMed2003

Species specificity in the activation of Xer recombination at dif by FtsK.

In Escherichia coli, chromosome dimers are resolved to monomers by the addition of a single cross-over at a specific locus on the chromosome, dif. Recombination is performed by two tyrosine recombinases, XerC and XerD, and requires the action of an additional protein, FtsK. We show that Haemophilus influenzae FtsK activates recombination by H. influenzae XerCD at H. influenzae dif. However, it cannot activate recombination by E. coli XerCD. Reciprocally, E. coli FtsK cannot activate recombination by the H. influenzae recombinases at H. influenzae dif. We took advantage of this species specificity to gain further insight into the mechanism of activation of Xer recombination at dif by FtsK. We mapped the region of FtsK implicated in species specificity to the extreme 140-amino-acid C-terminal residues of the protein. Our results suggest that FtsK interacts directly with XerCD in order to activate recombination at dif.

Enzyme Activation↗

PubMed2002

The effects of fish oil and isoflavones on delayed onset muscle soreness.

INTRODUCTION/PURPOSE: Fish oils (FO) have been shown to modulate the inflammatory response through alteration of the eicosanoid pathway. Isoflavones (ISO) appear to reduce the inflammatory pathway through their role as a tyrosine kinase inhibitor. Delayed onset muscle soreness (DOMS) develops after intense exercise and has been associated with an inflammatory response. Therefore, we hypothesized that physical parameters associated with DOMS could be decreased via the modulation of the inflammatory response by supplementing subjects with either FO or ISO. METHODS: 22 subjects were recruited and randomly assigned to one of three treatment groups: FO (1.8 g of omega-3 fatty acids x d(-1)), ISO (120 mg soy isolate x d(-1)), or placebo (PL) (Western fat blend and/or wheat flour). All treatment groups received 100-IU vitamin E x d(-1) to minimize lipid peroxidation of more highly unsaturated fatty acids. Subjects were supplemented 30 d before the exercise and during the week of testing and were instructed to refrain from unusual exercise. DOMS was induced by 50 maximal isokinetic eccentric elbow flexion contractions. Strength parameters, pain, arm circumference, and relaxed arm angle (RANG) were measured at 48, 72, and 168 h post exercise. Cortisol, creatine kinase (CK), interleukin-6 (IL-6), tumor necrosis factor (TNFalpha), malondialdehyde (MDA), and serum iron were measured before supplementation, after supplementation, and post exercise. RESULTS: Significant decreases were observed in RANG and strength 48 h postexercise among all groups, and there were significant increases in pain and arm circumference. There were no significant changes among all groups from baseline at 168 h (7 d) post exercise. There were no significant treatment effects between groups for the physical parameters or for cortisol, CK, IL-6, TNFalpha, MDA, or serum iron. CONCLUSION: These data indicate FO or ISO, at the doses supplemented, were not effective in ameliorating DOMS with the above-cited protocol.

Adult↗