An additional DNA element that binds RNA polymerase is found in some strong promoters, for example, those directing expression of the ribosomal RNA (rRNA) genes. This is called an UP-element and increases polymerase binding by providing an additional specific interaction between the enzyme and the DNA.

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#Id: 8456

#Unit 1. Molecules and their Interaction Relevant to Biology

The α helices have rotation of 100 degree per amino acid

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#Unit 1. Molecules and their Interaction Relevant to Biology

Gly is often observed at the C-cap & N cap both positions, Pro at the Ncap and Asp and Glu at N2 and N3.

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#Unit 1. Molecules and their Interaction Relevant to Biology

Helix can form in polypeptides consisting of either L- or D-amino acids but never exist to contain both types.

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#Id: 8459

#Unit 1. Molecules and their Interaction Relevant to Biology

Five types of constraints affect the stability of an  helix: 

(1) the intrinsic propensity of an amino acid residue to form an  helix; 

(2) the interactions between R groups, particularly those spaced three (or four) residues apart; 

(3) the bulkiness of adjacent R groups; 

(4) the occurrence of Pro and Gly residues; and 

(5) interactions between amino acid residues at the ends of the helical segment and the electric dipole inherent to the  helix.

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#Unit 1. Molecules and their Interaction Relevant to Biology

The intrinsic propensity of an amino acid residue to form an  helix

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#Id: 8461

#Unit 1. Molecules and their Interaction Relevant to Biology

The interactions between R groups, particularly those spaced three (or four) residues apart; The assembly is said to have a coiled coil structure because each α helix itself follows a helical path.