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Probing the importance and potential roles of the binding of the PH-domain protein Boi1 to acidic phospholipids.

ABSTRACT: BACKGROUND:The related proteins Boi1 and Boi2, which appear to promote polarized growth in S. cerevisiae, both contain a PH (pleckstrin homology) and an SH3 (src homology 3) domain. Previously, we gained evidence that a PH domain-bearing segment of Boi1, which we call Boi1-PH, is sufficient and necessary for function. In the current study, we investigate the binding of Boi1's PH domain to the acidic phospholipids PIP2 (phosphatidylinositol-4,5-bisphosphate) and PS (phosphatidylserine). RESULTS:Boi1-PH co-sediments with PS vesicles. It does so more readily when these vesicles contain a small amount of PIP2. Boi1-PH is degraded in yeast extracts in a manner that is stimulated by PIP2. Amino-acid substitutions that diminish binding to PIP2 and PS impair Boi1 function. Fusion to a myristoyl group-accepting sequence improves to different degrees the ability of these different mutant versions of Boi1-PH to function. Boi1 and Boi2 are localized to the periphery of buds during much of the budding cycle and to necks late in the cell cycle. Amino-acid substitutions that diminish binding to PIP2 and PS impair localization of Boi1 to the bud, but do not affect the localization of Boi1 to the neck. Conversely, a mutation in the SH3 domain prevents the localization of Boi1 to the neck, but does not impair localization to the bud. CONCLUSIONS:Boi1's PH domain binds to acidic phospholipids, and this binding appears to be important for Boi1 function. The main role of binding to PS may simply be to promote the association of the PH domain with membrane. The higher-affinity binding to PIP2, which apparently promotes a conformational change in the PH domain, may play an important additional role. Boi1 and Boi2 are localized to sites of polarized growth. Whereas the SH3 domain is needed for localization of Boi1 to the neck, the phospholipid-binding portion of the PH domain is important for localization to the bud.

SUBMITTER: Hallett MA

PROVIDER: S-EPMC117597 | biostudies-literature | 2002 Jun

REPOSITORIES: biostudies-literature

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Probing the importance and potential roles of the binding of the PH-domain protein Boi1 to acidic phospholipids.

Hallett Mark A MA Lo H Shuen HS Bender Alan A

BMC cell biology 20020627

<h4>Background</h4>The related proteins Boi1 and Boi2, which appear to promote polarized growth in S. cerevisiae, both contain a PH (pleckstrin homology) and an SH3 (src homology 3) domain. Previously, we gained evidence that a PH domain-bearing segment of Boi1, which we call Boi1-PH, is sufficient and necessary for function. In the current study, we investigate the binding of Boi1's PH domain to the acidic phospholipids PIP2 (phosphatidylinositol-4,5-bisphosphate) and PS (phosphatidylserine).<h ...[more]

PMID: 12097146

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Project description:The binding performance of dissolved organic matters (DOM) plays a critical role in the migration, diffusion and removal of various residual pollutants in the natural water environment. In the current study, four typical DOMs (including bovine serum proteins BSA (proteins), sodium alginate SAA (polysaccharides), humic acid HA and fulvic acid FA (humus)) are selected to investigate the binding roles in zwitterionic tetracycline (TET) antibiotic under various ionic strength (IS = 0.001-0.1 M) and pH (5.0-9.0). The dialysis equilibration technique was employed to determine the binding concentrations of TET, and the influence of IS and pH on binding performance was evaluated via UV-vis spectroscopy, total organic carbon (TOC), and Excitation-Emission-Matrix spectra (EEM), zeta potentials and molecule size distribution analysis. Our results suggested that carboxyl and phenolic hydroxyl were identified as the main contributors to TET binding based on the fourier transform infrared spectroscopy (FTIR) analysis, and the binding capability of four DOMs followed as HA > FA » BSA > SAA. The biggest binding concentrations of TET by 10 mg C/L HA, FA, BSA and SAA were 0.863 μM, 0.487 μM, 0.084 μM and 0.086 μM, respectively. The higher binding capability of HA and FA is mainly attributed to their richer functional groups, lower zeta potential (HA/FA = -15.92/-13.54 mV) and the bigger molecular size (HA/FA = 24668/27750 nm). IS significantly inhibits the binding interaction by compressing the molecular structure and the surface electric double layer, while pH had a weak effect. By combining the Donnan model and the multiple linear regression analysis, a modified Karickhoff model was established to effectively predict the binding performance of DOM under different IS (0.001-0.1 M) and pH (5.0-9.0) conditions, and the R2 of linear fitting between experiment-measured logKDOC and model-calculated logKOC were 0.94 for HA and 0.91 for FA. This finding provides a theoretical basis for characterizing and predicting the binding performance of various DOMs to residual micropollutants in the natural water environment.

Dataset Information

Probing the importance and potential roles of the binding of the PH-domain protein Boi1 to acidic phospholipids.

Publications

Probing the importance and potential roles of the binding of the PH-domain protein Boi1 to acidic phospholipids.

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