肽链信号序列是指什么 具体位置

肽链信号序列是指什么 具体位置
肽链信号序列是指什么 具体位置

肽链信号序列是指什么 具体位置
信号肽signal peptide：常用来特指指导蛋白质跨过内质网的信号.从更广泛的意义上讲,信号肽指的是指导蛋白质寻靶的任何一段连续的氨基酸序列.信号肽假说认为,编码分泌蛋白的mRNA在翻译是首先合成的是N末端带有疏水氨基酸残基的信号肽,它被内质网膜上的受体识别并与之相结合.信号肽经由膜中蛋白质形成的孔道到达内质网内腔,随后被位于腔表面的信号肽酶水解,由于它的引导,新生的多肽就能够通过内质网膜进入腔内,最终被分泌到胞外.
一般信号肽多在蛋白质的N末端.但是出现在C端的也有.还有核定位信号肽则可能出现在蛋白质肽链的任何部位.这是我根据维基百科总结的,不嫌累的话可以自己直接看英文.
Endoplasmic reticulum
Almost all proteins that are transported to the endoplasmic reticulum have a sequence consisting of 5-10 hydrophobic amino acids on the N-terminus.
The protein is guided to the ER by a signal-recognition particle (SRP),which moves between the ER and the cytoplasm.It binds to the signal peptide.The SRP binds to the signal peptide as soon as it is synthesized and extruded from the ribosome.This causes a pause in protein synthesis,most probably allowing the ribosome-SRP complex time to bind to the SRP receptor on the target ER membrane.The SRP protein is thought to be a regulatory GTP protein.Conformational changes may therefore lead to the SRP release.The protein may then be threaded through the ER membrane by a translocator pore.
Most of these proteins are transported from the endoplasmic reticulum to the Golgi apparatus.If these proteins have a particular 4-amino-acid retention sequence,KDEL (lys-asp-glu-leu),on the C-terminus,they are retained in the endoplasmic reticulum or are routed back to the ER (in instances where they escape) via interaction with the KDEL receptor in the Golgi apparatus.
[edit] Nucleus
Main article:nuclear localization signal
A nuclear localization signal (NLS) is a signal peptide directing to the nucleus and is often a unit consisting of five basic,plus-charged amino acids.The NLS normally is located anywhere on the peptide chain.
[edit] Nucleolus
The nucleolus within the nucleus can be targeted with a sequence called a nucleolar localization signal (abbreviated NoLS or NOS).
[edit] Mitochondrial matrix
The signal peptide that directs to the mitochondrial matrix has a sequence consisting of an alternating pattern (amphipathic helix)with a few hydrophobic amino acids and a few plus-charged amino acids at the N terminus.It is usually called the mitochondrial targeting signal (MTS).
[edit] Peroxisome
There are two types of signal peptides directing to peroxisome,which are called peroxisomal targeting signals (PTS).One is PTS1,which is made of three amino acids on the C-terminus.The other is PTS2,which is made of a 9-amino-acid sequence often present on the N-terminus of the protein.