Promote proliferation

Explanation

2. ion channel ion channel ionic spread

ion channel ionic spread (Facilitated Diffusion Through Ion Channel, also known as channel transport, refers to a transmembrane transport process with an ionic ion (such as sodium ion, potassium ion, calcium ion, chloride ion, etc.) with a concentration gradient or potential gradient.

Ion vector

ion vector, is hydrophobic small molecule, soluble in a lipid layer, increasing the transfer rate of the transfer ion, and is more microorganisms. It is a weapon for microbial defense to prey or compete with other species. The

ion carrier is also transporting ions in passive transportation, which can be divided into a movable ion carrier and channel ion carrier (CHANNEL FORMER). Two categories:

Availability ion vector: Valinomycin can bind K + on one side of the film, follow the electrochemical gradient through the lipid double layer, release K + on the other side of the film And can be carried out. The mechanism of action is like the siphon can make the water in the glass across the cup wall barrier and flow to the low. In addition, 2,4-dinitrophenol (DNP), carbonyl-cyanide-pair-trifluoromethythane (FCCP) can be transported H +, Ionomycin, A23187 can be transported Ca2 +.

Figure 5-2 Molecular Structure

Channel ion vector of prolinal:, such as short peptide, 2 molecules, 2 molecules, respectively, 3 molecules, 2 molecules such as shorthane peptide A (Grantin) The short bacillope peptide forms a transmembrane passage, which is selected to make the unit price cation such as H +, Na +, K + by the chemical gradient through the film, which is unstable, constantly forming and disintegrating, which is much higher than the movable ion vector .

Some of the characteristics of iouitation diffusion as an intermediary:

1, the various carrier proteins of the structural specific membrane and the substance therebetween and the substances thereof are highly structurally specific Sex, that is, only the substances of the specific structure can be transported.

2, the saturation phenomenon of the film is increased by more than a certain limit, and the transfer rate is no longer increased.

3, competitive suppression If a carrier has a substance similar to the two structures of A and B, it will be transported to the B substance will attenuate the transfer of A substances.

Channel protein

Channel protein is a hydrophilic passage across the textured membrane, allowing the appropriate size ion-concentration gradient to pass, so that the ion channel is also known. Some channels of channel proteins are typically in an open state, such as potassium leakage channels, allowing potassium ions to continuously flow. Some channel proteins are usually closed, that is, "door" is not continuous, only open under certain stimulation, and is instantaneous open instantaneous closure, in a few milliseconds, some ions, metabolites or other solutes are concentrated The gradient is free to diffuse through the cell membrane, which is also known as the gate channel (Gated Channel).

door channel can be divided into four categories: ligand gaNel, potential gate channel, cyclic nucleotide-ga-channel (Cyclic Nucleotide-galed Ion Channels) and Machinery Mechanosensitive Channel.

Channel

Different passages are different from the permeability of different ions, ie ion selectivity. This is determined by the structure of the channel, only allowing ions having a specific ionic radius and charge. Depending on ion selectivity, channels can be divided into sodium channels, calcium channels, potassium channels, chlorine channels, and the like. However, the ion selectivity of the channel is only relative rather than absolute, for example, in addition to the main permeation of Na +, the sodium channel is transparent to NH4 +, even slightly transmitted to K +.

ligand gate passage

Surface receptor combined with extracellular specific substances (ligand Ligand), causing the constructive change of the gate channel protein, as a result, "door" is opened, and Ion channel type receptor. Divided into a cationic channel such as acetylcholine, glutamate, and pyrolymine receptor, and an anionic passage, such as glycine and gamma-aminobutyric acid receptors.

n-type acetylcholine receptor [1] is to understand more of a type of ligand gate passage. It is a 5 polymer consisting of four different subunits, with a total molecular weight of about 290kD. The subunit is formed by a non-covalent bond such as hydrogen bonding, forming a plum-like passage-like structure having a structure α2βγδ, wherein the two alpha subunits are parts that bind to two molecule ACH.

ACH gate channel has three states: on, turn off and inactivation. When the two alpha subunits of the receptor bind ACH, causing a channel conformation change, the passage instantaneously opens, the membrane Na + internal flow, the inner K + external flow. The inner and outer potential difference of the membrane is adjacent to 0 values, forming a final board potential, and then causes a muscle cell action potential, muscle contraction. That is, when combined with the ACH, the ACH gate channel is also in the state of opening and closing alternating, only the probability of opening is large (90%). After the ACH is released, it is instantly hydrolyzed by acetylcholine esterase, and the passage is closed in about 1 millisecond. If the ACH is too long (about 20 milliseconds), the channel will be inactive.

Tube arrow and α silver ring snake toxins can be combined with acetyl choline receptor, but cannot open the channel, resulting in muscle paralysis.

Potential gate channel

Potential gate channel (VLtage Gated Channel) is when the concentration of intracellular or extracellular acetal ion is changed, or when the film potential is caused by other stimuli, Its conformation changes, "door" opens. Such as: Neuromuscular contacts are open from the ACH gating channel, this potential change can cause the potential door Na + channel present in adjacent muscle cell membranes and K + channels to activate (ie, open), causing myocyte action Potential; the action potential is transmitted to the muscle net, the Ca2 + channel opens causing Ca2 + outflow, which causes muscle contraction.

According to the structural analysis of Na +, K +, Ca2 + channel protein, it is found that the amino acid arrangement in the primary structure has considerable homology, belonging to the same protein family, is evolved by the same farm gene. Come. The K + potential gate channel consists of four α subunit (I-IV), each of which (S1-S6) transmembrane alpha spiral sections, N and C end are located in cytoplasmic surfaces. Connecting the S5-S6 segment of the hair chick (P zone or H5 region), the liner constituting the channel, the size can allow K + through.

k + channel has three states: turning on, off and inactivation. It is believed that the S4 segment is a voltage sensor, S4 height conserved, which belongs to a hydrophobic fragment, but every two hydrophobic residues have a positively charged arginine or lysine residue. The positive charge on the S4 segment may be a gantry charge. When the membrane is removed (the film is negative, the film is positive), causing a positively charged amino acid residue to turn the outer side surface, the channel protein conformation change, "door "Open, a large number of K + external flow, which is equivalent to the free spread of K +. K + potential door is just an instant (about a few milliseconds), and then inactivation. At this time, the spherical structure of the N-terminal is blocked in the center of the channel, the channel is inactive, and the sphere is released later, the "door" is closed.

The potassium ion channel KCSA of Streptomyces Lividans is also composed of four subunits, but each subunit has only two transmembrane fragments, and the structure is more simple. In 1998, Roderick Mackinnon et al. Obtained a high-resolution KCSA channel image with X-ray diffraction techniques, and the ionic selectivity of ion transmissivity was found to occur mainly in a narrow selective filter. The selective filter is 1.2 nm long and the pore size is about 0.3 nm (k + dehydration diameter diameter diameter diameter diameter diameter), and there is a string potassium-specific binding site, thereby only potassium ions can "queue" through the passage.

Tetrodotoxin, TTX) can block the sodium channel, the toxin positively charged guanphi extends into the ionic selective filter of the sodium channel, and the free carboxyl group on the inner wall of the channel, the remainder of the toxin The outer end of the passage is blocked, hinders sodium ions to enter, resulting in muscle paralysis.

Ring nucleotide door channel

is closely related to the voltage gathered channel family, from the protein sequence, they are similar to the voltage of the potassium channel, also The six transmembrane fragments are each having a charged fragment, and the P region constitutes the inner side of the aperture, and the entire channel is a tetramer structure. In the CNG channel, the C-terminus within the cell is longer, and the binding site of the cyclic nucleotide is contained.

Ring nucleotide door channel is distributed in a chemical sensor and a photoreceptor, related to the conversion of the film outside the membrane. For example, the g protein coupled receptor in the odor molecule is combined with a G protein coupled receptor in the chemical susceptor, activates CAMP, and opens CAMP gated cation channel, causing sodium ion internal flow, membrane Deficiency, producing nerve impulses, and finally forms an olfactory or taste.

Mechanical gate channel

cells can accept a wide variety of mechanical force stimulation, such as friction, pressure, pull tension, gravity, shear, and the like. The cells convert mechanical stimulating signals into electrochemical signals finally causing cellular reactions, referred to as mechanical signal transduction (MECHANOTRANSDUCTION).

There are two types of mechanical gate channels, one is to pull the activation or inactivated ion channel, and the other is a shear-sensitive ion channel, and the former is almost in all cell membranes. There are more vascular endothelial cells, cardiomyocytes, and capillaries in the inner ear, which only found in endothelial cells and cardiomyocytes. Talking-sensitive ion channels refers to ion channels that are directly opened or closed by the cell membrane. It is characterized by no selectivity, no direction, nonlinear, and latency. This channel is a 2 price or 1 price of cationic channels, which are Na +, K +, Ca2 +, mainly Ca2 +. The study shows that when the endothelial cells are pulled, the Ca2 + internal flow is caused by open, which is increased by Ca2 + mediated vascular active substance, and Ca2 + can also be used as intracellular beliefs, resulting in a further reaction.

Listening of the top of the inner ear cells is also a sensitive device that is sensitive to pull tension. When the hair curming is listened, the hair cells will have a temporary susceptor potential. From listening, the membrane of the root is heard, and there is only a very short incubation period, only a very short incubation period,

Water channel

long-term Since, the water molecules inside and outside the cells generally believe that the water molecules in a simple diffusion pass through the lipid double layer film. Later, some cells were highly permeable to water in the low levy solution, which is difficult to explain. If the red blood cell is moved into a low-permeable solution, it is quickly absorbed and hemolysis, and the oocytes of the aquatic animals do not expand in the low levy solution. Therefore, in addition to simply spreading the transmembrane transport in addition to simple diffusion, there is a special mechanism and proposes the concept of water channels.

In 1988, AGRE found a 28 kD hydrophobic transmembrane protein, called CHIP28 (Channel-Forming Integral Membrane Protein), CHIP28 in 1991 CDNA sequence, AGRE injected CHIP28 mRNA into an oocyte in African jaws, in low levy solution, oocytes quickly expanded, and cracked in 5 minutes, purified CHIP28 was placed in a liposome, and it obtained The same result. Such water absorption expansion of cells will be inhibited by Hg2 +, which is known to inhibit water through the treatment measures. This finding reveals that there is indeed a water passage on the cell membrane, and AGRE thus shares the 2003 Nobel Chemical Award with Researcher Roderick Mackinnon in the ion channel.

Found

The protein has been found in human cells, which is named water channel protein (AQUAPORIN, AQP), and has selective molecules. Through the characteristics. 35 such water channels have been found in Experimental Plant Arabidopsis (Arabidopsis Thaliana).

The activity adjustment of the water channel may have the following way: by phosphorylation to enhance the activity of AQP; varying the content of AQP on the membrane through film running transport, such as vascular presstuff (anti-continentine) to the kidney Tongtui and set cells epithelial cell water permeable; by regulating gene expression, the synthesis of AQP is promoted.

There are two passive diffusion for simple diffusion and promotion, and the same point is not required to consume ATP.

Promotes the diffusion as simple diffusion, with some of the following features:

1 promotes the help of proliferation requires the help of membrane proteins, and a few quantities in the speed of simple diffusion.

2 Simple diffusion rate is proportional to the concentration of the solute, while the promotion of the membrane protein helps can reach the maximum, when the transmembrane concentration of the solute reaches a certain degree, the speed of promoting diffusion is no longer improved. .

3 In simple diffusion, the structure is similar to the film by a substantially the same speed, and in promoting diffusion, the transportation protein has a high degree of selectivity. If transportation proteins can help glucose transport, but does not help with glucose transport similar to glucose structure.

4 is different from simple diffusion, and the promotion of transportation proteins will also be inhibited. The transportation of membrane transportation proteins is also subject to competitive inhibition similar to enzyme, as well as inhibitory effects of protein degenerative agents.