Stabilization of Profilin I and II by Poly-L-Proline

Profilins are small, 14- to 17-kDa proteins found in Plants, yeast, fungi, protozoa, mouse, human and certain viruses. Originally, profilin was identified to be involved in actin polymerization and its role established as a key regulator of F-actin dynamics. Apart from actin sequestering and polymerization, profilin plays several roles and has multiple binding partners. In Human, there are at least four isoforms of profilin, among them profilin I is expressed in all tissues, whereas other isoforms are tissue specific. Profilin II is brain specific and shown to be required for the neuronal development. In neuronal cells profilin II was shown to interact with ligands involved in signal transduction, membrane trafficking and vesicle recycling such as ROCK2, synapsins, POP-130/CyFIPI and dynamin 1. Profilins bind poly-L-proline (PLP) rich sequences and many proteins containing proline-rich stretches have been identified as potential ligands. ... The influence of PLP in profilin's structure and stability has not been investigated. Using fluorescence and Circular Dichroism we show that PLP extrinsically stabilizes Profilin in chemical denaturation experiments.