The intestinal fatty acid binding protein (I-FABP) belongs to a family of 15 kDa clamshell-like proteins that are found in many different tissues. So far, nine types have been identified. Their primary structures are highly conserved between species but somewhat less so among the different types. The function of these proteins, many of which are highly expressed, is not well understood. Their ability to bind lipid ligands suggests a role in lipid metabolism, but direct evidence for this idea is still lacking. We tested the hypothesis that I-FABP serves an essential role in the assimilation of dietary fatty acids by disrupting its gene (Fabpi) in the mouse. We discovered that Fabpi-/- mice are viable, but they display alterations in body weight and are hyperinsulinemic. Male Fabpi-/- mice had elevated plasma triacylglycerols and weighed more regardless of the dietary fat content. In contrast, female Fabpi-/- mice gained less weight in response to a high-fat diet. The results clearly demonstrate that I-FABP is not essential for dietary fat absorption. We propose that I-FABP functions as a lipid-sensing component of energy homeostasis that alters body weight gain in a gender-specific fashion.

The complete nucleotide sequence of the Staphylococcus aureus transposon Tn554, which encodes resistance to erythromycin and spectinomycin, was determined by the dideoxy chain termination method. The transposon was found to be 6691 bp in length and to contain six open reading frames of greater than 125 amino acids. Small insertion and deletion mutations were obtained in each of these by in vitro mutagenesis at restriction endonuclease cleavage sites and the mutants characterized with respect to transposition functions and antibiotic resistance markers. Three of the reading frames, designated tnpA, tnpB and tnpC, encode functions that are required for transposition of Tn554; genetic analysis indicated that these three genes define distinct complementation groups of transposition‐defective mutants. Two of the open reading frames correspond to the resistance determinants spc and ermA, the sixth, designated ORF, has no known function. Tn554‐specific peptides corresponding to tnpA, and spc were identified in a coupled transcription‐translation system in vitro.

We have determined which amino acids contribute to the pharmacophore of human C5a, a potent inflammatory mediator. A systematic mutational analysis of this 74-amino acid protein was performed and the effects on the potency of receptor binding and of CSa-induced intracellular calcium ion mobilization were measured. This analysis included the construction of hybrids between C5a and the homologous but unreactive C3a protein and sitedirected mutagenesis. Ten noncontiguous amino acids from the structurally well-defined 4-helix core domain (amino acids 1-63) and the C-terminal arginine-containing tripeptide were found to contribute to the pharmacophore of human C5a. The 10 mostly charged amino acids from the core domain generally made small incremental contributions toward binding affinity, some of which were independent. Substitutions of the C-terminal amino acid Arg 74 produced the largest single effect. We also found the connection between these 2 important regions to be unconstrained.

The importance of lowering serum cholesterol levels for the prevention of cardiovascular disease has been well documented. Because mevalonate pyrophosphate decarboxylase is a unique enzyme in the cholesterol biosynthetic pathway it is a potential therapeutic target for the treatment of hypercholesterolemia and other diseases. For this reason we cloned and expressed the cDNA for the human enzyme. We also cloned and expressed the yeast homolog using the human enzyme's similarity to a previously unidentified and incomplete genomic sequence. Northern blot analysis revealed a transcript of approximately 2 kilobases in a variety of human tissues. The recombinant human enzyme is a homodimer of 43-kDa subunits with a specific activity of 2.4 units/mg. Computer searches for similarity with known sequences showed that mevalonate pyrophosphate decarboxylase has little similarity to other proteins.

Mevalonate pyrophosphate decarboxylase was isolated from rat liver to 90% purity as judged by SDS-PAGE using Phenyl Sepharose, p-coumaric acid-Sepharose, Mono P, and Mono Q chromatography. Gel filtration chromatography of the crude extract determined the native enzyme to be near 100 kDa while SDS-PAGE of the purified enzyme showed a protein band at 45 kDa. This implies that the native rat liver enzyme is a homodimer which differs from the published report that the enzyme is a tetramer of 35 kDa subunits. We measured a specific activity of 4.6 units/mg and a KM for mevalonate pyrophosphate of 20 microM. These values are similar to those reported for the chicken liver and the pig liver enzymes, but differ from the published report of the rat liver enzyme.