Baeteriorhodopsin is a protein of light-dependent proton pump present in the purple membrane of Halobacterium salinarium. The L intermediate which arises in the microsecond time range is active complex to transmit the light energy absorbed in the chromophore to the protein. The Schiff base forms strong H-bonding to Asp85 with an intervention of a strongly H-bonding water molecule. This causes distortion in the chromomere to induce the proton transfer from the Schiff base to Asp85. The subsequent protein change in the site far from the Schiff base-Asp85 region is induced at the L stage already. Several lines of evidence suggest that energy transmission in rhodopsin proceeds in a similar way to bacteriorhodopsin.
A brief description is made to explain various iron-sulfur proteins which are widely distributed in various organisms and functioning in diverse metabolic systems. It includes the types of iron-sulfur cluster, classification of the iron-sulfur proteins based on the numbers of iron and sulfur atoms and the functions of these proteins. Model drawings of three dimensional structures are shown for several typical iron-sulfur proteins.
Specific and interchangeable association of α-helix chains by hydrophobic and ionic interaction is discussed mainly for the assembly of αn, βn and γn subchains into various laminin isoforms. Sequence of laminin subchains suggests that the hydrophobic surface of α-helix formed by non-polar amino acids at positions a and d in (abcdefg)n heptad repeat is major force of interchain interaction but the ionic edges formed by charged amino acids at positions e and g determine the specificity of interaction.