C7 protein
Encyclopedia
C7 protein is an engineered
zinc finger protein
based on the murine ZFP, Zif268
and discovered by Wu et al. in 1994 (published in 1995). It shares the same zinc finger
2 and zinc finger 3 of Zif268, but differs in the sequence of finger 1. It also shares the same DNA target, 5'-GCGTGGGCG-3'.
The shared sequences in single letter amino acid codes of fingers 2 and 3 are RSD-H-LTT and RAD-E-RKR (positions -1 through 6 in the alpha helix).
Zinc finger 1 has the sequence KSA-D-LKR which provides a 13-fold increase in affinity to the target sequence of the entire ZFP over that of Zif268.
It is used in zinc finger investigations in which the amino acid sequence of finger 2 is changed in order to determine the appropriate sequence to target a given three-nucleotide target site. A variation of C7, C7.GAT
is preferred since it lacks the aspartic acid
residue present in finger 3 of C7 and known to cause a phenomenon called 'target site overlap'. In this case the target site overlap is a result of the aspartic acid residue forming a hydrogen bond with the N4 of the cytosine (in the opposite strand) base-paired to the guanine in the finger 2 subsite. It can also form the same hydrogen bond with an adenine base paired to a thymine. This target site overlap would dictate that either a cytosine or adenine residue be present as the 3' nucleotide in the finger 2 subsite which is unacceptable when looking to target sequences containing another nucleotide at this position.
Protein engineering
Protein engineering is the process of developing useful or valuable proteins. It is a young discipline, with much research taking place into the understanding of protein folding and recognition for protein design principles....
zinc finger protein
Zinc finger protein
A zinc finger protein is a DNA-binding protein domain consisting of zinc fingers ranging from two in the Drosophila regulator ADR1, the more common three in mammalian Sp1 up to nine in TFIIIA...
based on the murine ZFP, Zif268
Zif268
EGR-1 also known as Zif268 or NGFI-A is a protein that in humans is encoded by the EGR1 gene....
and discovered by Wu et al. in 1994 (published in 1995). It shares the same zinc finger
Zinc finger
Zinc fingers are small protein structural motifs that can coordinate one or more zinc ions to help stabilize their folds. They can be classified into several different structural families and typically function as interaction modules that bind DNA, RNA, proteins, or small molecules...
2 and zinc finger 3 of Zif268, but differs in the sequence of finger 1. It also shares the same DNA target, 5'-GCGTGGGCG-3'.
The shared sequences in single letter amino acid codes of fingers 2 and 3 are RSD-H-LTT and RAD-E-RKR (positions -1 through 6 in the alpha helix).
Zinc finger 1 has the sequence KSA-D-LKR which provides a 13-fold increase in affinity to the target sequence of the entire ZFP over that of Zif268.
It is used in zinc finger investigations in which the amino acid sequence of finger 2 is changed in order to determine the appropriate sequence to target a given three-nucleotide target site. A variation of C7, C7.GAT
C7.GAT protein
The C7.GAT protein is a zinc finger protein based on the C7 protein . It features an alternative zinc finger 3 alpha helix sequence, preventing the target site overlap caused by the aspartic acid residue of the finger 3 of C7. The sequence of this third finger is TSG-N-LVR according to the single...
is preferred since it lacks the aspartic acid
Aspartic acid
Aspartic acid is an α-amino acid with the chemical formula HOOCCHCH2COOH. The carboxylate anion, salt, or ester of aspartic acid is known as aspartate. The L-isomer of aspartate is one of the 20 proteinogenic amino acids, i.e., the building blocks of proteins...
residue present in finger 3 of C7 and known to cause a phenomenon called 'target site overlap'. In this case the target site overlap is a result of the aspartic acid residue forming a hydrogen bond with the N4 of the cytosine (in the opposite strand) base-paired to the guanine in the finger 2 subsite. It can also form the same hydrogen bond with an adenine base paired to a thymine. This target site overlap would dictate that either a cytosine or adenine residue be present as the 3' nucleotide in the finger 2 subsite which is unacceptable when looking to target sequences containing another nucleotide at this position.