THE EFFECTS OF A MARATHON RACE ON RUNNING ECONOMY AND LEG MUSCULAR STRENGTH AND POWER

INTRODUCTION: Previous studies have reported that running economy as well as leg muscular strength and power decrease after a marathon race(Nicol et al., 1991 ; Chevrolet et al. 1993). However, the relationship between the change in running economy and the change in muscular strength and power is still unclear. Therefore, the purpose of this study was to examine the effects of a marathon race on running economy, as well as leg muscular strength and power. Relationships among race performance, decrease in running economy and decrease in leg muscular strength and power were also investigated. METHODS: Thirteen healthy males performed treadmill running (200 m/min., 3 min.), isometric knee extension (3s), counter-movement-jump and 5-series-jumps 3-1 day(s) before (PRE) and immediately after (POST) participating in either the 1996 or 1997 "Tsukuba marathon race (42.195 km) ". RESULTS: 1) Mean race time of the marathon was 2 hours 57 minutes 39 seconds. Average running speed during the latter half of the race was significantly lower than the former half . 2) In comparison to PRE, oxygen consumption during treadmill running in POST increased significantly while maximal strength of isometric knee extension, jumping height of counter-movement-jump and jumping height of 5-series-jumps decreased significantly . 3) There were no relationships between percent change ((Post-Pre)/Pre x 100) in oxygen consumption during treadmill running and percent change in leg muscular strength and power. 4) There was a significant correlation between percent change ((Latter- Former)/Former x 100) in running speed during the race and percent change in jumping height of counter-movement-jump (r=0.541). However, no significant relationship was observed between percent change in running speed and percent change in running economy. CONCLUSION: Running a marathon race decreases both running economy and muscular strength and power but these seem to be caused by different mechanisms. The decrease in leg muscular strength and power during the marathon race seems have been an influence on the decrease in running speed during the latter half of the race. REFERENCES Chevrolet et al. (1993) Med. Sci. Sports Exerc. 25:501-507. Nicol et al. (1991) Scand. J. Sports Med. 1:195-204

Constant Enthalpy Change Value during Pyrophosphate Hydrolysis within the Physiological Limits of NaCl

A decrease in water activity was thought to result in smaller enthalpy change values during PPi hydrolysis, indicating the importance of solvation for the reaction. However, the physiological significance of this phenomenon is unknown. Here, we combined biochemistry and calorimetry to solve this problem using NaCl, a physiologically occurring water activity-reducing reagent. The pyrophosphatase activities of extremely halophilic Haloarcula japonica, which can grow at ∼4 m NaCl, and non-halophilic Escherichia coli and Saccharomyces cerevisiae were maximal at 2.0 and 0.1 m NaCl, respectively. Thus, halophilic and non-halophilic pyrophosphatases exhibit distinct maximal activities at different NaCl concentration ranges. Upon calorimetry, the same exothermic enthalpy change of −35 kJ/mol was obtained for the halophile and non-halophiles at 1.5–4.0 and 0.1–2.0 m NaCl, respectively. These results show that solvation changes caused by up to 4.0 m NaCl (water activity of ∼0.84) do not affect the enthalpy change in PPi hydrolysis. It has been postulated that PPi is an ATP analog, having a so-called high energy phosphate bond, and that the hydrolysis of both compounds is enthalpically driven. Therefore, our results indicate that the hydrolysis of high energy phosphate compounds, which are responsible for biological energy conversion, is enthalpically driven within the physiological limits of NaCl.This work was supported by Grant-in-aid for Scientific Research on Innovative Areas 20118005 from the Ministry of Education, Culture, Sports, Science, and Technology of Japan

Selected Mutations in a Mesophilic Cytochrome c Confer the Stability of a Thermophilic Counterpart

Mesophilic cytochrome c551 of Pseudomonas aeruginosa (PA c551) became as stable as its thermophilic counterpart, Hydrogenobacter thermophilus cytochrome c552 (HT c552), through only five amino acid substitutions. The five residues, distributed in three spatially separated regions, were selected and mutated with reference to the corresponding residues in HT c552 through careful structure comparison. Thermodynamic analysis indicated that the stability of the quintuple mutant of PA c551 could be partly attained through an enthalpic factor. The solution structure of the mutant showed that, as in HT c552, there were tighter side chain packings in the mutated regions. Furthermore, the mutant had an increased total accessible surface area, resulting in great negative hydration free energy. Our results provide a novel example of protein stabilization in that limited amino acid substitutions can confer the overall stability of a natural highly thermophilic protein upon a mesophilic molecule.This work was supported by a grant from the Japanese Ministry of Education, Science and Culture

Difference in NaCl tolerance of membrane-bound 5′-nucleotidases purified from deep-sea and brackish water Shewanella species

Shewanella species are widely distributed in sea, brackish, and fresh water areas, growing psychrophilically or mesophilically, and piezophilically or piezo-sensitively. Here, membrane-bound 5′-nucleotidases (NTases) from deep-sea Shewanella violacea and brackish water Shewanella amazonensis were examined from the aspect of NaCl tolerance in order to gain an insight into protein stability against salt. Both NTases were single polypeptides with molecular masses of ~59 kDa, as determined on mass spectroscopy. They similarly required 10 mM MgCl2 for their activities, and they exhibited the same pH dependency and substrate specificity for 5′-nucleotides. However, S. violacea 5′-nucleotidase (SVNTase) was active enough in the presence of 2.5 M NaCl, whereas S. amazonensis 5′-nucleotidase (SANTase) exhibited significantly reduced activity with the same concentration of the salt. Although SVNTase and SANTase exhibited high sequence identity (69.7%), differences in the ratio of acidic to basic amino acid residues and the number of potential salt bridges maybe being responsible for the difference in the protein stability against salt. 5′-Nucleotidases from these Shewanella species will provide useful information regarding NaCl tolerance, which may be fundamental for understanding bacterial adaptation to growth environments.This work was supported by a Grant-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology of Japan [No. 26240045], a grant from the Japan Society for the Promotion of Science [No. 25-1446], and The Salt Science Research Foundation [No. 1655]

Topologically Linked Crystals

We discovered a new class of topological crystals, namely linked rings of crystals. Two rings of tantalum triselenide (TaSe3) single crystals were linked to each other while crystal growing. The topology of the crystal form is called a "Hopf link", which is the simplest link involving just two component unknots linked together exactly once. The feature of the crystals is not covered by the conventional crystallography.Comment: 6 pages, 3 figures, to appear in J. Crystal Growt

Motion of rotatory molecular motor and chemical reaction rate

We examine the dependence of the physical quantities of the rotatory molecular motor, such as the rotation velocity and the proton translocation rate, on the chemical reaction rate using the model based only on diffusion process. A peculiar behavior of proton translocation is found and the energy transduction efficiency of the motor protein is enhanced by this behavior. We give a natural explanation that this behavior is universal when certain inequalities between chemical reaction rates hold. That may give a clue to examine whether the motion of the molecular motor is dominated by diffusion process or not.Comment: 12 pages, 8 figure

Stabilization of Pseudomonas aeruginosa Cytochrome c551 by Systematic Amino Acid Substitutions Based on the Structure of Thermophilic Hydrogenobacter thermophilus Cytochrome c552

A heterologous overexpression system for mesophilic Pseudomonas aeruginosa holocytochrome c551 (PA c551) was established using Escherichia coli as a host organism. Amino acid residues were systematically substituted in three regions of PA c551 with the corresponding residues from thermophilic Hydrogenobacter thermophilus cytochrome c552 (HT c552), which has similar main chain folding to PA c551, but is more stable to heat. Thermodynamic properties of PA c551 with one of three single mutations (Phe-7 to Ala, Phe-34 to Tyr, or Val-78 to Ile) showed that these mutants had increased thermostability compared with that of the wild-type. Ala-7 and Ile-78 may contribute to the thermostability by tighter hydrophobic packing, which is indicated by the three dimensional structure comparison of PA c551 with HT c552. In the Phe-34 to Tyr mutant, the hydroxyl group of the Tyr residue and the guanidyl base of Arg-47 formed a hydrogen bond, which did not exist between the corresponding residues in HT c552. We also found that stability of mutant proteins to denaturation by guanidine hydrochloride correlated with that against the thermal denaturation. These results and others described here suggest that significant stabilization of PA c551 can be achieved through a few amino acid substitutions determined by molecular modeling with reference to the structure of HT c552. The higher stability of HT c552 may in part be attributed to some of these substitutions.This work was supported in part by grants from the Japanese Ministry of Education, Science and Culture

Five Amino Acid Residues Responsible for the High Stability of Hydrogenobacter thermophilus Cytochrome c552

Five amino acid residues responsible for extreme stability have been identified in cytochrome c552 (HT c552) from a thermophilic bacterium, Hydrogenobacter thermophilus. The five residues, which are spatially distributed in three regions of HT c552, were replaced with the corresponding residues in the homologous but less stable cytochrome c551 (PA c551) from Pseudomonas aeruginosa. The quintuple HT c552 variant (A7F/M13V/Y34F/Y43E/I78V) showed the same stability against guanidine hydrochloride denaturation as that of PA c551, suggesting that the five residues in HT c552 necessarily and sufficiently contribute to the overall stability. In the three HT c552 variants carrying mutations in each of the three regions, the Y34F/Y43E mutations resulted in the greatest destabilization, by –13.3 kJ mol–1, followed by A7F/M13V (–3.3 kJ mol–1) and then I78V (–1.5 kJ mol–1). The order of destabilization in HT c552 was the same as that of stabilization in PA c551 with reverse mutations such as F34Y/E43Y, F7A/V13M, and V78I (13.4, 10.3, and 0.3 kJ mol–1, respectively). The results of guanidine hydrochloride denaturation were consistent with those of thermal denaturation for the same variants. The present study established a method for reciprocal mutation analysis. The effects of side-chain contacts were experimentally evaluated by swapping the residues between the two homologous proteins that differ in stability. A comparative study of the two proteins was a useful tool for assessing the amino acid contribution to the overall stability.This work was supported in part by grants from Hiroshima University, the Noda Institute for Scientific Research, and the Japanese Ministry of Education, Science and Culture (grants-in-aid for Scientific Research on Priority Areas)

Structural and functional insights into thermally stable cytochrome c' from a thermophile

Thermophilic Hydrogenophilus thermoluteolus cytochrome c0 (PHCP) exhibits higher thermal stability than a mesophilic counterpart, Allochromatium vinosum cytochrome c0 (AVCP), which has a homo-dimeric structure and ligand-binding ability. To understand the thermal stability mechanism and ligand-binding ability of the thermally stable PHCP protein, the crystal structure of PHCP was first determined. It formed a homo-dimeric structure, the main chain root mean square deviation (rmsd) value between PHCP and AVCP being 0.65 A ° . In the PHCP structure, six specific residues appeared to strengthen the heme-related and subunit–subunit interactions, which were not conserved in the AVCP structure. PHCP variants having altered subunit–subunit interactions were more severely destabilized than ones having altered heme-related interactions. The PHCP structure further revealed a ligand-binding channel and a penta-coordinated heme, as observed in the AVCP protein. A spectroscopic study clearly showed that some ligands were bound to the PHCP protein. It is concluded that the dimeric PHCP from the thermophile is effectively stabilized through heme-related and subunit–subunit interactions with conservation of the ligand-binding ability.This work was performed under the Cooperative Research Program of the “Network Joint Research Center for Materials and Devices”

Understanding the apparent stator-rotor connections in the rotary ATPase family using coarse-grained computer modeling

Advances in structural biology, such as cryo-electron microscopy (cryo-EM) have allowed for a number of sophisticated protein complexes to be characterized. However, often only a static snapshot of a protein complex is visualized despite the fact that conformational change is frequently inherent to biological function, as is the case for molecular motors. Computer simulations provide valuable insights into the different conformations available to a particular system that are not accessible using conventional structural techniques. For larger proteins and protein complexes, where a fully atomistic description would be computationally prohibitive, coarse-grained simulation techniques such as Elastic Network Modeling (ENM) are often employed, whereby each atom or group of atoms is linked by a set of springs whose properties can be customized according to the system of interest. Here we compare ENM with a recently proposed continuum model known as Fluctuating Finite Element Analysis (FFEA), which represents the biomolecule as a viscoelastic solid subject to thermal fluctuations. These two complementary computational techniques are used to answer a critical question in the rotary ATPase family; implicit within these motors is the need for a rotor axle and proton pump to rotate freely of the motor domain and stator structures. However, current single particle cryo-EM reconstructions have shown an apparent connection between the stators and rotor axle or pump region, hindering rotation. Both modeling approaches show a possible role for this connection and how it would significantly constrain the mobility of the rotary ATPase family