소수성 분석을 통한 막단백질의 이동신호서열에 대한 연구

Abstract

Membrane proteins are encoded by 20-30% of most genomes and play pivotal roles in numerous cellular activities in various cellular and subcellular membranes. Accordingly, in eukaryotic cells, the biogenesis of organellar proteins is an essential process requiring their correct localization among various cellular and subcellular membranes. Therefore, there are specific targeting mechanisms to deliver proteins to appropriate subcellular compartments. Localization of these proteins is determined by either cotranslational or posttranslational mechanisms, depending on the final destination. However, it is not fully understood how the targeting specificity of membrane proteins is determined in plant cells. Here, I investigate the mechanism by which signal-anchored (SA) proteins are differentially targeted to the endoplasmic reticulum (ER) or endosymbiotic organelles using in vivo targeting, subcellular fractionation, and bioinformatics approaches. For targeting SA proteins to endosymbiotic organelles, the C-terminal positively charged region (CPR) flanking the transmembrane domain (TMD) is necessary but not sufficient. The hydrophobicity of the TMD in CPR-containing proteins also plays a critical role in determining targeting specificity

TMDs with a hydrophobicity value >0.4 on the Wimley and White (WW) scale are targeted primarily to the ER, whereas TMDs with lower values are targeted to endosymbiotic organelles. Based on these data, I propose that the CPR and the hydrophobicity of the TMD play a critical role in determining the targeting specificity between the ER and endosymbiotic organelles. In addition, I suggest that the WW hydrophobicity scale can be applied as the important decoding tool to decipher the molecular code within signal sequences and understand trafficking mechanisms of membrane proteins.