New way of protein modification: stearoylation

We learned the prefixes for lipid in Lesson 14-3. They are:

adip(o)-, lip(o)-, pi(o)-, pimel(o)-, stear(o)-, steat(o)-

One of the prefixes, stear(o)- is used in stearic acid. There is a paper on Nature that is related to stearic acid in 2015.

In this paper, the research team discovered that the activity of human transferrin receptor 1 (TFR1) can be affected by stearoylation. The stearoylated TFR1 cannot activate JNK protein so mitochondria will not become fragmented.

Because fragmented mitochondria is poorly functional, stearoylation is actually a good thing in this aspect.

What is stearic acid? Stearic acid is a long-chain fatty acid, with 18 carbons with no double bond. We usually express fatty acid as "C18:0", meaning this fatty acid has 18 carbons with no double bond. The structure of stearic acid can be seen in the picture below:

Stearic acid. Source: wikipedia

Stearoylation is a whole new way of protein modification. We knew phosphorylation, ubiquitination and glycosylation can affect protein activity. But stearoylation is the first time.

To make this story more interesting, the whole discovery was started on a mistake. So making mistakes isn't so bad sometimes, huh?

Reference:

Teleman A.A. et. al., 2015. Regulation of mitochondrial morphology and function by stearoylation of TFR1. Nature. doi:10.1038/nature14601

硬脂酸化（stearoylation）：新的調節蛋白質活性的方法

我們在第十四課（三）裡面介紹了跟脂肪（lipid）相關的字首：

adip(o)-, lip(o)-, pi(o)-, pimel(o)-, stear(o)-, steat(o)-

這些字首裡面，stear(o)-與硬脂酸(stearic acid）有關。最近，有一篇論文就是與硬脂酸有關的。

在這篇論文裡，研究團隊發現，人類第一型運鐵蛋白受器（TFR1，human transferrin receptor 1)會因為被硬脂酸化（stearoylation）而影響它的活性，使它不能再活化JNK蛋白，最後使得粒線體免於破碎化（fragmentation）的命運。

粒線體破碎化會發生什麼事呢？粒線體如果破碎化，功能就會變得很差；所以這麼看來，硬脂酸還真的是好東西呢！它是長鏈的飽和脂肪酸（C18:0，意為十八個碳沒有雙鍵、三鍵的脂肪酸），結構如下：

硬脂酸。圖片來源：wiki

所謂的硬脂酸化，就是除了上圖最左邊的-OH基以外，整個十八個碳加上一個氧都轉到蛋白質上面去了。這個發現可是非常非常新，過去我們知道加上磷酸根（磷酸化，phosphorylation）、加上泛素（泛素化，ubiquitination）、加上糖（糖基化，glycosylation）會影響蛋白質活性，但是加上硬脂酸可還真的是頭一遭呢！

有意思的是，這個發現，竟然是從泡錯培養基開始的！可見有時候泡錯藥也不見得是壞事？（大誤）哈哈！

參考文獻：

Miscellaneous999。無心插柳之硬脂酸（stearic acid）抑制粒線體破碎化。