A small-molecule activator of kinesin-1 drives remodeling of the microtubule network

The microtubule motor kinesin-1 interacts via its cargo-binding domain with both microtubules and organelles, and hence plays an important role in controlling organelle transport and microtubule dynamics. In the absence of cargo, kinesin-1 is found in an autoinhibited conformation. The molecular basis of how cargo engagement affects the balance between kinesin-1's active and inactive conformations and roles in microtubule dynamics and organelle transport is not well understood. Here we describe the discovery of kinesore, a small molecule that in vitro inhibits kinesin-1 interactions with short linear peptide motifs found in organelle-specific cargo adaptors, yet activates kinesin-1's function of controlling microtubule dynamics in cells, demonstrating that these functions are mechanistically coupled. We establish a proof-of-concept that a microtubule motor-cargo interface and associated autoregulatory mechanism can be manipulated using a small molecule, and define a target for the modulation of microtubule dynamics

Garlic Revisited: Antimicrobial Activity of Allicin-Containing Garlic Extracts against Burkholderia cepacia Complex

The antimicrobial activities of garlic and other plant alliums are primarily based on allicin, a thiosulphinate present in crushed garlic bulbs. We set out to determine if pure allicin and aqueous garlic extracts (AGE) exhibit antimicrobial properties against the Burkholderia cepacia complex (Bcc), the major bacterial phytopathogen for alliums and an intrinsically multiresistant and life-threatening human pathogen. We prepared an AGE from commercial garlic bulbs and used HPLC to quantify the amount of allicin therein using an aqueous allicin standard (AAS). Initially we determined the minimum inhibitory concentrations (MICs) of the AGE against 38 Bcc isolates; these MICs ranged from 0.5 to 3% (v/v). The antimicrobial activity of pure allicin (AAS) was confirmed by MIC and minimum bactericidal concentration (MBC) assays against a smaller panel of five Bcc isolates; these included three representative strains of the most clinically important species, B. cenocepacia. Time kill assays, in the presence of ten times MIC, showed that the bactericidal activity of AGE and AAS against B. cenocepacia C6433 correlated with the concentration of allicin. We also used protein mass spectrometry analysis to begin to investigate the possible molecular mechanisms of allicin with a recombinant form of a thiol-dependent peroxiredoxin (BCP, Prx) from B. cenocepacia. This revealed that AAS and AGE modifies an essential BCP catalytic cysteine residue and suggests a role for allicin as a general electrophilic reagent that targets protein thiols. To our knowledge, we report the first evidence that allicin and allicin-containing garlic extracts possess inhibitory and bactericidal activities against the Bcc. Present therapeutic options against these life-threatening pathogens are limited; thus, allicin-containing compounds merit investigation as adjuncts to existing antibiotics

MICs (µg/ml) of AGE for <i>B. cepacia</i> complex.

<p>* <b>We have included all codes to avoid confusion between Edinburgh strain collection numbers, LMG and ATCC codes.</b></p><p>MICs (µg/ml) of AGE for <i>B. cepacia</i> complex.</p

MICs and MBCs (µg/ml) of AAS for <i>B. cepacia</i> complex.

<p>MICs and MBCs (µg/ml) of AAS for <i>B. cepacia</i> complex.</p

Chemical structure of allicin and mechanism of formation from alliin by the enzyme alliinase.

<p>Step 1. Alliinase hydrolyses alliin to produce allylsulfenic acid which, in step 2, condenses spontaneously with the loss of water to produce allicin.</p

HPLC and MS analysis of aqueous allicin standard (AAS) and aqueous garlic extract (AGE).

<p>(A) AAS was analysed using a C18 reverse phase column with UV detection at 240 nm. The standard eluted at 4.1 minutes. AAS had an observed <i>m/z</i> of 185.0067 (consistent with the [M+Na]⁺ species; theoretical <i>m/z</i> 185.0065; [C₆H₁₀OS₂+Na]⁺) (<i>inset</i>). (B) AGE was analysed by the same method as described for AAS. The peak at 4.1 minutes corresponds to the mass of allicin.</p