N-TERMINAL PLACED SIGNAL SEQUENCES DO NOT AFFECT THE TOPOLOGY OF PASSENGER PROTEINS

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: MON 515-547-Female Reproductive Endocrinology
Basic/Translational
Monday, June 17, 2013: 1:45 PM-3:45 PM
Expo Halls ABC (Moscone Center)

Poster Board MON-523
Jasmeet Kaur*1, Ray Rudolph2 and Himangshu S Bose3
1Mercer Univ Sch of Med, Savannah, GA, 2Memorial University Medical Center, Savannah, GA, 3Mercer Univ Schl of Med, Savannah, GA
Targeting of proteins to their ultimate destination has important role in their proper functioning. Mistargeting of proteins leads to physiological malfunctions. Endoplasmic reticulum (ER) is primary site for targeting of newly synthesized proteins by signal (targeting) sequences. In our study, we show that wild-type proteins retain their topology even when placed behind signal sequences with completely opposite topology. The intact signal sequence of the passenger protein overrides the sequence in front of them and decides the topology of the protein. In our study, the signal anchor region of aromatase lost its function completely and was cleaved as part of the signal sequence when fused in front of a secretory protein, preprolactin (pPL). The signal anchor region of aromatase even after having the site for glycosylation was not glycosylated and also translocation of passenger protein was not blocked. Thus the site of signal sequence cleavage of pPL was exposed to the ER lumen and generated soluble secretory protein. Similarly when signal sequence of pPL was fused in front of wild-type aromatase, an integral membrane protein was generated, instead of a soluble protein. These results show that the intact signal sequences and signal anchors with their passenger proteins are active even at internal sites i.e other than the N-terminal. Thus, the wild type proteins retain their targeting capacities even when a powerful signal with completely opposite topology is placed in front of them.

Nothing to Disclose: JK, RR, HSB

*Please take note of The Endocrine Society's News Embargo Policy at http://www.endo-society.org/endo2013/media.cfm