BIOMG 1350 Chapter Notes - Chapter 15: Transmembrane Protein, Signal Recognition Particle, Signal Peptidase
3 Oct 2016
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Proteins are transported into organelles by three mechanisms: synthesis begins on ribosomes, sorting signal. Directs protein to organelle in which it is required. Into: the nucleus, mitochondria, chloroplasts, peroxisomes, er: nuclear pores. Selective gates that actively transport specific macromolecules. Also allow free diffusion of smaller molecules: er, mitochondria, chloroplasts. Transported protein must unusually unfold to snake across membrane through translocator: one endomembrane system to another/moving onward from er. Pinch off from membrane of one compartment and then fuse with membrane of second. Signal sequences direct proteins to the correct compartment: srp. Continuous stretch of amino acids (15-60) on protein. Removed from finished protein once it has been sorted (usually) Necessary and sufficient to direct protein to destination: deleting signal sequence from er cytosolic protein, signal sequence at beginning redirects to the er, srp with same destination can vary greatly. Physical properties difference: hydrophobicity and placement of charged amino acids. Proteins enter the nucleus through nuclear pores: nuclear envelope.
