Structural Features of Beta-Strands in Proteins
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Questions and Answers

The F1 component of the ATP synthase enzyme has 3 β subunits with each adopting a different ______ at a given time (loose, open, and tight conformations).

conformation

The hydrophobic effect stabilizes ______ structure.

protein

Aromatic R Groups can contribute to the ______ effect.

hydrophobic

Cys can form ______ bonds.

<p>disulfide</p> Signup and view all the answers

Cys has a positive hydropathy index, classified as polar due to its SH group's ability to act as a weak acid and be involved in weak ______ bonds.

<p>hydrogen</p> Signup and view all the answers

Amphitropic Proteins have a reversible lipid attachment process, where the lipid attachment is __________

<p>covalently</p> Signup and view all the answers

B-strands never occur singly, but always as part of a ________

<p>sheet</p> Signup and view all the answers

In a b-strand, each residue extends ________ Ã…

<p>3.5</p> Signup and view all the answers

β-barrel proteins have no unpaired hydrogen bonding main chain groups, making them suitable as __________ proteins

<p>membrane</p> Signup and view all the answers

All b-barrel membrane proteins have an even number of b-strands, reflecting the requirement that they be inserted ________

<p>pairwise</p> Signup and view all the answers

Since side chains in a beta strand project alternately on either side, all hydrophobic residues fall on one side and the hydrophilic residues fall on the other side of the ________ strand

<p>beta</p> Signup and view all the answers

The hydrophobic side faces the __________ and the hydrophilic side faces the interior of the barrel.

<p>exterior</p> Signup and view all the answers

Even number of strands in OMP structures results in strands that do not ______ each other.

<p>cross</p> Signup and view all the answers

Periplasmic loops in OMP structures are often very ______, sometimes forming β-turns.

<p>short</p> Signup and view all the answers

Barrels with 8-10 strands in OMP structures have a solid core filled with ______ residues.

<p>hydrophilic</p> Signup and view all the answers

Intermediate-sized b-barrels with 16-18 strands in OMP structures have aqueous pores generally with inserted ______.

<p>loops</p> Signup and view all the answers

Large barrels with 22–26 b-strands in OMP structures generally have a plug domain that ______ into and closes most of the channel.

<p>inserts</p> Signup and view all the answers

Match the OMP structure characteristics with their corresponding descriptions:

<p>Even number of strands = Results in strands that do not cross each other Antiparallel β sheet = All b-strands in OMP structures are arranged in this manner Extracellular loops are often long = Characteristic feature of OMP structures with 16-18 strands Periplasmic loops are very short = Common in OMP structures such as OmpX with 8 strands</p> Signup and view all the answers

Match the OMP examples with their respective number of beta strands:

<p>OmpX = 8 strands OmpF = 18 strands FepA = 22 strands VDAC = Odd number of beta strands</p> Signup and view all the answers

Match the OMP structure sizes with their corresponding features:

<p>Barrels with 8-10 strands = Have a solid core filled with hydrophilic residues Intermediate sized b-barrels with 16-18 strands = Have aqueous pores generally with inserted loops Large barrels with 22–26 b-strands = Generally have a plug domain that inserts into and closes most of the channel VDAC - voltage-dependent anion channel = Made up of an odd number of beta strands</p> Signup and view all the answers

Match the location descriptions to the corresponding termini in OMP structures:

<p>N and C-termini always periplasmic and next to each other = Characteristic positioning in OMP structures Helix at N-terminus inserts into pore = Specific feature observed in certain OMP structures Most abundant OM protein in eukaryotic mitochondria = VDAC - voltage-dependent anion channel Acts as an ion channel; also plays a role in apoptosis = VDAC - voltage-dependent anion channel</p> Signup and view all the answers

Match the residue types to their location in the beta-barrel structure:

<p>Hydrophobic residues = Found on the side facing the exterior of the barrel Hydrophilic residues = Found on the side facing the interior of the barrel Interior residues = Residues within the beta-barrel structure Bilayer facing residues = Residues facing the lipid bilayer</p> Signup and view all the answers

Match the amino acid property with its corresponding description:

<p>Negatively Charged R Groups = Can form ionic bonds Aromatic R Groups = Can contribute to the hydrophobic effect Polar, Uncharged R Groups = R groups can form hydrogen bonds Nonpolar, aliphatic R groups = Contribute to hydrophobic effect</p> Signup and view all the answers

Match the protein symmetry with its example:

<p>Quasi-symmetry = F1 component of the ATP synthase enzyme Anti-parallel symmetry = VDAC protein</p> Signup and view all the answers

Match the number of beta strands with the corresponding OMP structure size:

<p>8-10 strands = Small barrels with a solid core filled with hydrophobic residues 22–26 strands = Large barrels generally with a plug domain that closes most of the channel</p> Signup and view all the answers

Match the location in a beta strand with its characteristic feature:

<p>Hydrophobic side = Faces the lipid bilayer Hydrophilic side = Faces the interior of the barrel</p> Signup and view all the answers

Match the residue type with its specific location in a beta-barrel structure:

<p>Cys = Located in positions where disulfide bonds can form Aromatic R Groups = Located to contribute to the hydrophobic effect</p> Signup and view all the answers

Match the effect with its role in stabilizing protein structure:

<p>The hydrophobic effect = Stabilizes protein structure</p> Signup and view all the answers

Match the amino acid classification with its rationale:

<p>Cys classified as polar = Due to its SH group's involvement in weak hydrogen bonds</p> Signup and view all the answers

Match the termini description with its corresponding location in OMP structures:

<p>Periplasmic loops = Often forming beta-turns</p> Signup and view all the answers

Match the number of subunits with their conformations in a protein complex:

<p>3 beta subunits = Adopting different conformations (loose, open, tight) at a given time</p> Signup and view all the answers

Match the lipid attachment process with its characteristic for Amphitropic Proteins:

<p>Reversible lipid attachment process = Where lipid attachment can occur</p> Signup and view all the answers

Match the following terms related to protein structure with their corresponding descriptions:

<p>Anti-parallel beta strands = Side chains project alternately on either side Hydrophobic effect = Stabilizes protein structure Polar, Uncharged R Groups = Can form hydrogen bonds Cys = Can form disulfide bonds</p> Signup and view all the answers

Match the following characteristics of VDAC (Voltage-Dependent Anion Channel) with their functions:

<p>Solid core filled with hydrophobic residues = Forms the interior of the barrel Aqueous pores in OMP structures = Generally have inserted proteins Plug domain in large barrels = Inserts into and closes most of the channel Reversible lipid attachment process = Characteristic of Amphitropic Proteins</p> Signup and view all the answers

Match the residue types with their specific locations in beta-barrel structures:

<p>Aromatic R Groups = Contribute to the hydrophobic effect Negatively Charged R Groups = Located on the hydrophilic side Positively Charged R Groups = Located on the hydrophilic side Cys = Classified as polar due to its weak acid ability</p> Signup and view all the answers

Match the following amino acid properties with their corresponding descriptions:

<p>Hydropathy index of Cys = Positive due to SH group's weak acid ability 20 naturally occurring amino acids = Include nonpolar, aliphatic R groups Quasi-symmetry proteins = Have multiple copies with different conformations F1 component of ATP synthase enzyme = Has 3 β subunits with different conformations</p> Signup and view all the answers

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