We present an updated analysis of the linker and core histone proteins and their proteoforms in the green microalga Chlamydomonas reinhardtii by top-down mass spectrometry (TDMS). The combination of high-resolution liquid chromatographic separation, robust fragmentation, high mass spectral resolution, the application of a custom search algorithm, and extensive manual analysis enabled the characterization of 86 proteoforms across all four core histones H2A, H2B, H3, and H4 and the linker histone H1. All canonical H2A paralogs, which vary in their C-termini, were identified, along with the previously unreported noncanonical variant H2A.Z that had high levels of acetylation and C-terminal truncations. Similarly, a majority of the canonical H2B paralogs were identified, along with a smaller noncanonical variant, H2B.v1, that was highly acetylated. Histone H4 exhibited a novel acetylation profile that differs significantly from that found in other organisms. A majority of H3 was monomethylated at K4 with low levels of co-occuring acetylation, while a small fraction of H3 was trimethylated at K4 with high levels of co-occuring acetylation.

我们对绿色微藻中的接头和核心组蛋白及其蛋白形式进行了更新分析莱茵衣藻通过自上而下的质谱（TDMS）。高分辨率液相色谱分离、稳定的碎裂、高质谱分辨率、自定义搜索算法的应用和广泛的手动分析相结合，能够对所有四个核心组蛋白 H2A、H2B、H3 和 H4 的 86 种蛋白质型进行表征，以及接头组蛋白 H1。鉴定了所有 C 端不同的规范 H2A 旁系同源物，以及以前未报道的具有高水平乙酰化和 C 端截断的非规范变体 H2A.Z。类似地，大多数典型的 H2B 旁系同源物被鉴定，以及一个高度乙酰化的较小的非典型变体 H2B.v1。组蛋白 H4 表现出与其他生物体中发现的显着不同的新型乙酰化谱。