Characteristics of Outer Membrane Proteins

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What is indicative of a transmembrane segment in a hydropathy plot?

A mix of hydrophilic and hydrophobic residues

More than 20 residues of low hydropathy index

Less than 10 residues of high hydropathy index

More than 20 residues of high hydropathy index (correct)

What is the mean hydrophobicity threshold according to Kyte Doolittle for predicting a transmembrane helix?

0.5

2.0

3.0

1.4 (correct)

What is the approximate free energy cost per residue to disrupt hydrogen bonds in the membrane?

~1 kcal/mol

~6 kcal/mol

~2 kcal/mol

~4 kcal/mol (correct)

What is the primary factor that drives the formation of an α-helix in a transmembrane segment?

Thermodynamics favoring α-helix formation Signup and view all the answers

What is the role of the dielectric constant in membrane proteins?

Insulates charges from one another Signup and view all the answers

What happens to non-polar domains in membranes due to their low dielectric constant?

They have a low ability to conduct charges Signup and view all the answers

In the context of hydropathy plots, what is the purpose of using a 'sliding window' technique?

To identify membrane-spanning sections in a protein Signup and view all the answers

What is the main purpose of the Kyte-Doolittle & Engelman-Steitz-Goldman scales in hydrophobicity analysis?

To calculate the free energy of transfer of amino acid side chains into water Signup and view all the answers

What does the hydropathy index reflect in the context of hydropathy plots?

The propensity of an amino acid to be hydrophobic Signup and view all the answers

When averaging the hydropathy index for successive segments of a polypeptide chain, what are these segments known as?

Hydropathy windows Signup and view all the answers

How is a 'window' defined in the context of hydropathy plots?

A specific range of amino acids chosen for averaging Signup and view all the answers

What information can be obtained by analyzing the hydropathy profile using a 'sliding window' technique?

Local hydrophobicity changes along the protein sequence Signup and view all the answers

Which of the following statements about polytopic membrane proteins is correct?

If a polytopic protein has an odd number of transmembrane segments, the N- and C-termini must be on the same side of the membrane. Signup and view all the answers

Which of the following scales is commonly used to generate hydropathy plots for predicting membrane protein topology?

The Kyte-Doolittle scale Signup and view all the answers

What is a key factor that contributes to the hydrophobicity of an amino acid residue?

All of the above factors contribute to determining the hydrophobicity of an amino acid residue. Signup and view all the answers

In the context of membrane protein topology prediction, what does the term 'hydropathy plot' refer to?

A plot of the hydrophobicity values of amino acids along the protein sequence. Signup and view all the answers

Which of the following statements about overexpression and purification of integral membrane proteins is correct?

Poly-His tags are commonly used for purification of overexpressed integral membrane proteins via immobilized metal affinity chromatography (IMAC). Signup and view all the answers

In the context of membrane protein topology prediction, what does an 'even number of transmembrane segments' typically imply?

The N- and C-termini of the protein must be on the same side of the membrane. Signup and view all the answers