Tutor profile: Jerry O.
What is the function of Selectivity Filters? What purpose do they serve in cellular signaling cascades?
The most well-known selectivity filter is the water-gated Aquaporins channel. It is an integral membrane protein that mediates the transport of water across the lipid membrane. What is unique about this protein its selectivity filter. Water molecules are propagated through the channel via a coordinated interaction between four conserved positively charged residues. Water are lined up such that the partially negative charged oxygen face the positive charges of the channel. Helical movement and overall conformational heterogeneity within its helices push water molecules through the channel. In this manner, only some water molecules propagate through the channel. The importance is that tight control of osmosis results in dynamic movements of other molecules such as proteins and other endogenous signaling molecules. In general, selectivity filters play a role in signaling cascades through interactions with signaling agents such as ligand binding and allosteric protein interactions.
What is the difference between the active site and the allosteric site for enzymes? How is the function behind both sites?
Traditionally, the active site is considered the catalytic domain of enzymes whereas the allosteric site is considered the regulatory domain. The active site is where the substrates bind, and where products leave. In contrast, the allosteric site responsible for controlling the amount of products formed, the speed of the product formation, and the communication with other molecules. Therefore, the allosteric site seems to be regulatory domains that help the active site. However, this is not true. Recent literature suggests the independent function of the allosteric site and how enzymes and proteins communicate to produce a cellular response. For instance, enzymes can mediate product formation through their allosteric sites instead of the active site. Binding at the active site sometimes does not produce tighter biding affinity between residues whereas binding of an allosteric molecule makes this possible.
What is the fundamental mechanism underlying cellular processes? What are the exceptions to this rule?
The fundamental mechanism for cellular processes comes from cell signaling cascades and cell-cell communication. Specifically, it is the association and dissociation between proteins and facilitates functions. The major exception to this rule is misfolded proteins that cause neurodegenerative diseases such as Alzheimer's, Parkinson, and Huntington's disease.
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