Which of the following DNA binding proteins contain a helix-turn-helix domain?
The Cro, CAP, and λ repressor proteins differ in size and tertiary structure but all bind to B-DNA as a dimer. Each contains a helix–turn–helix motif that is positioned along one face of the B-DNA at its major groove.
What is the average length of the α helical segments in the HTH motif?
Explanation: The average length of the α-helical segments in the H-T-H motif is about 7 – 9 amino acid residues. The H-T-H motif contains two short-helices. It is present in the DNA-binding domain of many bacterial regulatory proteins.
How do alpha helices bind to DNA?
The α-helix is a right-handed helix with the peptide bonds located on the inside and the side chains extending outward. It is stabilized by the regular formation of hydrogen bonds parallel to the axis of the helix; they are formed between the amino and carbonyl groups of every fourth peptide bond.
What is a helix-turn-helix DNA binding domain?
In proteins, the helix-turn-helix (HTH) is a major structural motif capable of binding DNA. Each monomer incorporates two α helices, joined by a short strand of amino acids, that bind to the major groove of DNA. It should not be confused with the helix–loop–helix motif.
How do DNA binding proteins recognize specific DNA sequences?
Basic Requirements for DNA Binding Proteins recognize a particular sequence by having a surface that is chemically complementary to that of the DNA, forming a series of favorable electrostatic and van der Waals interactions between the protein and the base pairs.
What region of DNA is most often targeted by DNA binding proteins?
B-DNA
DNA-binding proteins are proteins that have DNA-binding domains and thus have a specific or general affinity for single- or double-stranded DNA. Sequence-specific DNA-binding proteins generally interact with the major groove of B-DNA, because it exposes more functional groups that identify a base pair.
What are the three DNA binding structures?
Although each of these proteins has unique features, most bind to DNA as homodimers or heterodimers and recognize DNA through one of a small number of structural motifs. The common motifs include the helix-turn-helix, the homeodomain, the leucine zipper, the helix-loop-helix, and zinc fingers of several types.
How many complete turns of the helix are there in a typical keratin rod domain?
In a regular α-helix there are 3.6 residues per turn of the helix. In a left-handed coiled-coil there are 3.5 residues per turn. Thus, in a two chained coiled-coil there is a repeat pattern of seven residues that are represented by the letters a-b-c-d-e-f-g. Residues a and d in this pattern are hydrophobic.
How are alpha helices stabilized?
α-Helix Conformation The α-helix is a right-handed helix with the peptide bonds located on the inside and the side chains extending outward. It is stabilized by the regular formation of hydrogen bonds parallel to the axis of the helix; they are formed between the amino and carbonyl groups of every fourth peptide bond.
How do activators work?
Most activators function by binding sequence-specifically to a regulatory DNA site located near a promoter and making protein–protein interactions with the general transcription machinery (RNA polymerase and general transcription factors), thereby facilitating the binding of the general transcription machinery to the …
What type of helix is found in DNA?
The most common form of DNA which has right handed helix and proposed by Watson and Crick is called B-form of DNA or B-DNA . In addition, the DNA may be able to exist in other forms of double helical structure.
What is helix loop helix?
Basic helix-loop-helix structural motif of ARNT. Two α-helices (blue) are connected by a short loop (red). A basic helix-loop-helix (bHLH) is a protein structural motif that characterizes one of the largest families of dimerizing transcription factors. bHLH transcription factors are often important in development or cell activity.
What is the unit of DNA helix?
DNA is a long polymer made from repeating units called nucleotides. The structure of DNA is dynamic along its length, being capable of coiling into tight loops and other shapes. In all species it is composed of two helical chains, bound to each other by hydrogen bonds. Nov 21 2019
What is a single helix molecule called?
DNA is a double helix, while RNA is a single helix. Both have sets of nucleotides that contain genetic information. (Image credit: udaix Shutterstock) Deoxyribonucleic acid, or DNA, is a molecule that contains the instructions an organism needs to develop, live and reproduce.
