Jovcevski Blagojce, Kelly Megan A, Rote Anthea P, Berg Tracey, Gastall Heidi Y, Benesch Justin L P, Aquilina J Andrew, Ecroyd Heath
Illawarra Health and Medical Research Institute and School of Biological Sciences, University of Wollongong, Wollongong, NSW 2522, Australia.
Physical and Theoretical Chemistry Laboratory, Department of Chemistry, South Parks Road, Oxford OX1 3QZ, UK.
Chem Biol. 2015 Feb 19;22(2):186-95. doi: 10.1016/j.chembiol.2015.01.001.
Serine phosphorylation of the mammalian small heat-shock protein Hsp27 at residues 15, 78, and 82 is thought to regulate its structure and chaperone function; however, the site-specific impact has not been established. We used mass spectrometry to assess the combinatorial effect of mutations that mimic phosphorylation upon the oligomeric state of Hsp27. Comprehensive dimerization yielded a relatively uncrowded spectrum, composed solely of even-sized oligomers. Modification at one or two serines decreased the average oligomeric size, while the triple mutant was predominantly a dimer. These changes were reflected in a greater propensity for oligomers to dissociate upon increased modification. The ability of Hsp27 to prevent amorphous or fibrillar aggregation of target proteins was enhanced and correlated with the amount of dissociated species present. We propose that, in vivo, phosphorylation promotes oligomer dissociation, thereby enhancing chaperone activity. Our data support a model in which dimers are the chaperone-active component of Hsp27.
哺乳动物小热休克蛋白Hsp27在第15、78和82位残基处的丝氨酸磷酸化被认为可调节其结构和伴侣功能；然而，位点特异性影响尚未确定。我们使用质谱法评估模拟磷酸化的突变对Hsp27寡聚状态的组合效应。全面的二聚化产生了相对不拥挤的光谱，仅由偶数大小的寡聚体组成。一个或两个丝氨酸的修饰降低了平均寡聚体大小，而三突变体主要是二聚体。这些变化反映在修饰增加时寡聚体解离的倾向更大。Hsp27防止靶蛋白无定形或纤维状聚集的能力增强，且与存在的解离物种数量相关。我们提出，在体内，磷酸化促进寡聚体解离，从而增强伴侣活性。我们的数据支持一种模型，即二聚体是Hsp27的伴侣活性成分。
