SCP2 with other low molecular weight proteins

SCP2 amino acid composition is compared in Table 4 with the protein preparation of Dempsey [47]. As can be seen, marked differences exist in the amino acid compositions of these two proteins, particularly in the quantities of threonine, alanine, valine and leucine. Also, the leudne/isoleucine ratio for SCP2 was 2.04, while for the protein preparation of Dempsey it was 0.76. In addition, while arginine and tyrosine were present in the Dempsey protein preparation, none of these amino acids was found in SCP2. The correlation coefficient between SCP2 and the Dempsey protein preparation is 0.736. Clearly, SCP2 and the protein isolated by Dempsey and coworkers are separate and distinct proteins. 

Amino acid compositions of SCP2 and other low molecular weight proteins of interest 

The amino acid composition of purified SCP2 is also compared in Table 4 with the amino acid composition of FABP [48]. Marked differences exist in the abundance of threonine, alanine, valine and leucine. The correlation coefficient between SCPj and FABP is 0.732. Clearly, SCP and FABP are separate and distinct proteins. Furthermore, there is no immunological cross-reactivity between SCP2 and FABP, in an extremely sensitive enzyme-linked immunosorbent assay procedure. 

As seen in Table 4 the amino acid compositions of the Dempsey protein preparation [47] and FABP [48] are virtually identical. The correlation coefficient is 0.997. It is clear that the Dempsey protein preparation is identical to FABP [21,27,47,48]. 

When the release of cholesterol from adrenal cytoplasmic lipid inclusion droplets was measured as a function of either SCP2 or FABP concentration, there was a concentration-dependent release of cholesterol from the lipid inclusion droplets with SCPj, but not with FABP [50]. When pregnenolone production was measured there was a concentration-dependent formation of pregnenolone from endogenous mitochondrial cholesterol with SCP2, but not with FABP. In contrast, FABP, but not SCPj, induced a substantial increase in the release of labeled arachidonate from adrenal cytoplasmic lipid inclusion droplets, prelabeled with [l- C]arachidonate [50]. 

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Comparison of SCP2 with other low molecular weight proteins (a) Fatty-acid-binding protein (FABP)... 

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