CBR1의 세포 내 위치 전환을 통한 다양한 스트레스 적응 기작 동정

Abstract

The understanding of the protein targeting is important to decipher the accurate functions of proteins. Specially, the membrane protein trafficking is involved in complex mechanisms to localize to its destination. To achieve the minimal exposure to cytosol, cytosolic factors are tightly regulated with newly synthesized membrane proteins. Signal anchored proteins (SA) are famous membrane proteins which contain a transmembrane domain (TMD) in extreme N-terminal. SAs play critical roles in a translocon complex, a signal transduction and an electron transfer and they are employed as a model protein to study of the targeting signal of membrane proteins. Endoplasmic reticulum (ER) is the first station of membrane proteins which target to golgi apparatus, plasma membranes, tonoplasts, and peroxisomes. The signal peptides of ER SA proteins have high hydrophobic transmembrane domains (TMDs) which are recognized by signal recognition particle (SRP) for the ER membrane targeting. However, the known features of SA signal peptides and escort proteins such as SRP did not cover all of ER SA proteins targeting mechanisms, still now. In this study, I provide a novel pathway to target to ER membranes with cytochrome b5 reductase1 (CBR1), known as the ER SA protein. CBR1 had a mild hydrophobic TMD in its N-terminal and mainly exhibited mitochondria outer membrane localization in roots. Interestingly, CBR1 switched its localization from mitochondria outer membranes to ER membranes using the novel targeting mechanism in various stress conditions. In ER membranes, CBR1 participated the desaturation of fatty acids, leading to activation of PM H+-ATPases, Na+/H+ antiporters, rhizosphere acidification, and the facilitation of salt stress adaptation and iron uptake.