Altruism can proliferate through group/kin selection despite high random gene flow

The ways in which natural selection can allow the proliferation of cooperative behavior have long been seen as a central problem in evolutionary biology. Most of the literature has focused on interactions between pairs of individuals and on linear public goods games. This emphasis led to the conclusion that even modest levels of migration would pose a serious problem to the spread of altruism in group structured populations. Here we challenge this conclusion, by analyzing evolution in a framework which allows for complex group interactions and random migration among groups. We conclude that contingent forms of strong altruism can spread when rare under realistic group sizes and levels of migration. Our analysis combines group-centric and gene-centric perspectives, allows for arbitrary strength of selection, and leads to extensions of Hamilton's rule for the spread of altruistic alleles, applicable under broad conditions.Comment: 5 pages, 2 figures. Supplementary material with 50 pages and 26 figure

The Mode of Action of Recombinant Mycobacterium tuberculosis Shikimate Kinase: Kinetics and Thermodynamics Analyses

Tuberculosis remains as one of the main cause of mortality worldwide due to a single infectious agent, Mycobacterium tuberculosis. The aroK-encoded M. tuberculosis Shikimate Kinase (MtSK), shown to be essential for survival of bacilli, catalyzes the phosphoryl transfer from ATP to the carbon-3 hydroxyl group of shikimate (SKH), yielding shikimate-3-phosphate and ADP. Here we present purification to homogeneity, and oligomeric state determination of recombinant MtSK. Biochemical and biophysical data suggest that the chemical reaction catalyzed by monomeric MtSK follows a rapid-equilibrium random order of substrate binding, and ordered product release. Isothermal titration calorimetry (ITC) for binding of ligands to MtSK provided thermodynamic signatures of non-covalent interactions to each process. A comparison of steady-state kinetics parameters and equilibrium dissociation constant value determined by ITC showed that ATP binding does not increase the affinity of MtSK for SKH. We suggest that MtSK would more appropriately be described as an aroL-encoded type II shikimate kinase. Our manuscript also gives thermodynamic description of SKH binding to MtSK and data for the number of protons exchanged during this bimolecular interaction. The negative value for the change in constant pressure heat capacity (ΔCp) and molecular homology model building suggest a pronounced contribution of desolvation of non-polar groups upon binary complex formation. Thermodynamic parameters were deconvoluted into hydrophobic and vibrational contributions upon MtSK:SKH binary complex formation. Data for the number of protons exchanged during this bimolecular interaction are interpreted in light of a structural model to try to propose the likely amino acid side chains that are the proton donors to bulk solvent following MtSK:SKH complex formation. © 2013 Rosado et al

Double-reciprocal plots for steady-state kinetics of <i>Mt</i>SK using either ATP (A) or SKH (B) as the variable substrate.

<p>Each curve represents varied-fixed levels of the co-substrate, ranging from 37 to 4800 µM for SKH and from 9 to 1200 µM to ATP.</p

Thermodynamics parameters of formation of binary complexes between <i>Mt</i>SK and substrate(s) or product(s).

<p>K_D represents the equilibrium dissociation constant, ΔH is the binding enthalpy, ΔS is the binding entropy, ΔG is the Free Gibbs energy, and –TΔS is the negative term for temperature (in Kelvin) times binding entropy.</p

<i>Mt</i>SK:SKH thermodynamic binding parameters as a function of temperature (A) and binding enthalpy as a function of buffer ionization enthalpy at pH 7.6 (B).

<p><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0061918#pone-0061918-g007" target="_blank">Figure 7A</a> shows the ΔH (filled circles), -TΔS (open circles) and ΔG (inverted filled triangles) dependence on a temperature ranging from 10 to 40°C, which permits determination of a ΔC_p value of −320 (±16) cal mol⁻¹ K⁻¹. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0061918#pone-0061918-g007" target="_blank">Figure 7B</a> shows the dependence of observed enthalpy on buffer ionization enthalpy (ΔH_ion) at 25 °C. Data fitting to Eq. 6 yielded a value of −0.47 for N_H+ (number of protons exchanged during the binding process) and −2.2 kcal mol⁻¹ for ΔH_int (intrinsic enthalpy).</p

Shikimate Kinase catalyzed phosphoryl transfer from ATP to C3 hydroxyl group of shikimate (SKH), yielding shikimate 3-phosphate (S3P) and ADP.

<p>Shikimate Kinase catalyzed phosphoryl transfer from ATP to C3 hydroxyl group of shikimate (SKH), yielding shikimate 3-phosphate (S3P) and ADP.</p

12% SDS-PAGE analysis of pooled fractions of Mt<i>SK</i> for each purification step.

<p>Lane 1, Protein Molecular Weight Marker (Fermentas); lane 2, soluble <i>E. coli</i> BL21 (DE3) [pET-23a(+)::aroK] extract; lane 3, Soluble proteins after 10 mM MgCl₂ precipitation step; lane 4, Phenyl Sepharose 16/10; and lane 5, Sephacryl S-100 HR.</p