Structural Lipoprotein Peak 11 Protein

The existence of this peak was reported in 1969 by Inouye and Guthrie. However, this peak was identified only recently as the free form of a structural lipoprotein, which has been reported by Braun and his coworkers to bind covalently to the peptidoglycan. This lipoprotein is the most abundant protein in E. coli and an excellent membrane protein to investigate because of its many interesting characteristics. Indeed, this lipoprotein is one of the best studied membrane proteins. 

A more complex case is the serum lipoprotein (74), shown in Figure 13. When sonicated into water, total lipids from both the low density (/ ) and high density (a) lipoproteins give rise to the high resolution spectra expected of molecules which have a high degree of motion. The spectra of the native lipoproteins show line widths nearly identical to those of the lipids alone, so that no additional motional constraints of the apolar portions of the phospholipids occur when the lipids are bound to the apoproteins of the blood lipoproteins. All the obvious peaks observed in the native lipoproteins can be accounted for by lipid protons, and no upheld shift of the methylene protons occurs. We can conclude that unlike the case of the lysolecithin-serum albumin system, the bonding of lipids to proteins is not apolar. In the serum lipoproteins the NMR results are consistent with a micellar structure and not with extensive apolar association of lipid with protein. 

Extensive chemical analysis of peak 11 protein was also carried out in our laboratory from many standpoints, such as the amino acid composition, fatty acid content, and contents of the peptidoglycan components. These studies clearly demonstrated that the protein of peak 11 has the exact chemical structure as the lipoprotein shown in Fig. 9, except that it does not contain any components of the peptidoglycan. Furthermore, most recently, the peak 11 protein was highly purified, and its carboxyl-terminal amino acid sequence was identified as -Tyr-Arg-Lys. This is extremely important because this carboxyl-terminal sequence would not be expected if... 

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