Draw a rough diagram of the "salami sandwich" model to explain how adding tryptophan to the trp

Draw a rough diagram of the "salami sandwich" model to...

Key Concepts

Ligand Binding

Ligand binding is the process by which a molecule (ligand) specifically interacts with a particular site on a protein. This binding can stabilize certain conformations of the protein, triggering structural rearrangements that alter the protein's ability to interact with other molecules or DNA, thus affecting its regulatory function.

Regulatory Protein Mechanism

Many regulatory proteins function by adopting different conformations that determine their interaction with DNA or other cellular components. The binding of small effector molecules can shift these proteins from inactive to active forms (or vice versa), thereby serving as a critical mechanism in controlling gene expression and cellular responses.

Protein Conformational Change

This concept refers to how proteins can change their three-dimensional structure when they interact with specific molecules. Such changes in shape can switch a protein between functional and non-functional states, which is vital for regulating biological processes like gene expression and enzymatic activity.

Allosteric Regulation

Allosteric regulation involves the binding of a molecule at a site distinct from the active site, leading to a structural change that modulates the protein's activity. This mechanism allows cells to finely tune protein functions, often acting as an on/off switch in metabolic pathways and signal transduction.

Transcript

00:01 Okay, so in this video we're going to be talking about the tryptophan repressor in bacterial cells, and then we're going to be looking at a couple different modifications or mutant forms of this triptofan repressor and see what would happen to triptophan synthesis in the cell.

00:17 So bacterial cells can either take in triptophan from their environment or they can produce it internally.

00:23 So the way that they regulate this is through the triptophan repressor.

00:26 So for instance, if you had tryptophan in your environment, like in this case here, then the triptophan would bind to the triptophan repressor, which is this blue little box.

00:38 And when it binds to the repressor, the repressor is going to bind to dna.

00:43 Well, when it binds to the dna, rna polymerase cannot come in and bind to dna, so it is not going to be making enzymes for triptophan synthesis.

00:54 However, if you have low tryptophan in the environment and you need to be making some, then this triptophan repressor is not going to become activated.

01:03 It's going to stay in its inactive form, so it is not going to bind to the dna, and that allows rna polymerase to come in and bind to the dna.

01:12 So then they can make the enzymes needed for tryptophan synthesis.

01:17 So let's say we had a mutant version of this tryptophan repressor that could not bind to dna, even if it bound a tryptophan, it cannot bind a dna.

01:27 Well, you would always be stuck in this state right here, and you would always be making enzymes for triptophan synthesis because there's nothing blocking rna polymerase from sitting on the dna.

01:39 So you would always make tryptophan, even with high tryptophan in the environment.

01:49 Now, if you had a repressor that couldn't bind tryptophan, so you would always, again, be in this inactive state, because we know that tryptophan activates the repressor, then again you would be in this state where you would always have rna polymerase bound to the dna.

02:06 So again, you would always be making, always make tryptophan.

02:12 Now in the last example, the repressor can bind to the dna even without tryptophan.

02:18 So it doesn't matter if tryptophan is there or not.

02:21 It is always going to be bound to the dna.

02:23 So we're going to be over here like this.

02:25 So it is always reprimorrable.

02:26 Repressing tryptophan synthesis...