Conventional dogma presumes that protamine-mediated DNA compaction in sperm is achieved by passive electrostatics between DNA and the arginine-rich core of protamines. However, phylogenetic analysis reveals several non-arginine residues that are conserved within, but not across, species. The functional significance of these residues or post-translational modifications are poorly understood. Here, we investigated the functional role of K49, a rodent-specific lysine residue in mouse protamine 1 (P1) that is acetylated early in spermiogenesis and retained in sperm. In vivo, an alanine substitution (P1 K49A) results in ectopic histone retention, decreased sperm motility, decreased male fertility, and in zygotes, premature P1 removal from paternal chromatin. In vitro, the P1 K49A substitution decreases protamine-DNA binding and alters DNA compaction/decompaction kinetics. Hence, a single amino acid substitution outside the P1 arginine core is sufficient to profoundly alter protein function and developmental outcomes, suggesting that protamine non-arginine residues are essential to ensure reproductive fitness.

中文翻译：

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鱼精蛋白 1 中的单残基置换破坏小鼠精子基因组包装和胚胎发育

传统的教条假设精子中鱼精蛋白介导的 DNA 压缩是通过 DNA 和富含精氨酸的鱼精蛋白核心之间的被动静电实现的。然而，系统发育分析揭示了几个在物种内而不是跨物种保守的非精氨酸残基。这些残基或翻译后修饰的功能意义知之甚少。在这里，我们研究了 K49 的功能作用，K49 是小鼠鱼精蛋白 1 (P1) 中的一种啮齿动物特异性赖氨酸残基，它在精子发生的早期被乙酰化并保留在精子中。在体内，丙氨酸替代 (P1 K49A) 导致异位组蛋白保留、精子活力降低、男性生育能力降低，以及在受精卵中，P1 从父本染色质中过早去除。体外，P1 K49A 取代降低了鱼精蛋白与 DNA 的结合并改变了 DNA 压缩/分解动力学。因此，P1 精氨酸核心外的单个氨基酸取代足以深刻改变蛋白质功能和发育结果，表明鱼精蛋白非精氨酸残基对于确保生殖健康至关重要。