Gene_locus Report for: horse-2plrp

We report a high-quality draft sequence of the genome of the horse (Equus caballus). The genome is relatively repetitive but has little segmental duplication. Chromosomes appear to have undergone few historical rearrangements: 53% of equine chromosomes show conserved synteny to a single human chromosome. Equine chromosome 11 is shown to have an evolutionary new centromere devoid of centromeric satellite DNA, suggesting that centromeric function may arise before satellite repeat accumulation. Linkage disequilibrium, showing the influences of early domestication of large herds of female horses, is intermediate in length between dog and human, and there is long-range haplotype sharing among breeds.

Horse pancreatic lipase-related proteins PLRP1 and PLRP2 are produced by the pancreas together with pancreatic lipase (PL). Sequence-comparison analyses reveal that the three proteins possess the same two-domain organization: an N-terminal catalytic domain and a C-terminal domain, which in PL is involved in colipase binding. Nevertheless, despite the high level of sequence identity found, they exhibit distinct enzymatic properties. The intrinsic sensitivity of the peptide bond between Ser245 and Thr246 within the flap region of PLRP2 to proteolytic cleavage probably complicates PLRP2 crystallization since, as shown here, this proteolyzed form of PLRP2 is only crystallized after specific detergent stabilization of this region. This has been performed by the hanging-drop vapour-diffusion method at 291 K and exclusively in the presence of N,N-dimethyldecylamine-beta-oxide (DDAO). However, most crystals (>95%) are highly twinned and diffract poorly (to approximately 7-5 A resolution). Diffraction-quality trigonal crystals have unit-cell parameters a = b = 128.4, c = 85.8 A and belong to space group P3(2)21. A 2.9 A native data set was collected at ESRF on beamline ID14-2 with an R(merge) of 12.7%. Preliminary structural analysis provides a structural basis for the specific roles of DDAO.

Although structurally similar to pancreatic lipase (PL), the key enzyme of intestinal fat digestion, pancreatic lipase-related protein type 2 (PLRP2) differs from PL in certain functional properties. Notably, PLRP2 has a broader substrate specificity than PL, and unlike that of PL, its activity is not restored by colipase in the presence of bile salts. In the studies presented here, the activation mechanism of horse PLRP2 was studied through active site-directed inhibition experiments, and the results demonstrate fundamental differences with that of PL. The opening of the horse PLRP2 flap occurs as soon as bile salt monomers are present, is accelerated in the presence of micelles, and does not require the presence of colipase. Moreover, in contrast to PL, horse PLRP2 is able to directly interact with a bile salt micelle to form an active binary complex, without the micelle being presented by colipase, as evidenced by molecular sieving experiments. These findings, together with the sensitivity of the horse PLRP2 flap to partial proteolysis, are indicative of a higher flexibility of the flap of horse PLRP2 relative to PL. From these results, it can be concluded that PLRP2 can adopt an active conformation in the intestine, which could be important for the further understanding of the physiological role of PLRP2. Finally, this work emphasizes the essential role of colipase in lipase catalysis at the lipid-water interface in the presence of bile.

We report a high-quality draft sequence of the genome of the horse (Equus caballus). The genome is relatively repetitive but has little segmental duplication. Chromosomes appear to have undergone few historical rearrangements: 53% of equine chromosomes show conserved synteny to a single human chromosome. Equine chromosome 11 is shown to have an evolutionary new centromere devoid of centromeric satellite DNA, suggesting that centromeric function may arise before satellite repeat accumulation. Linkage disequilibrium, showing the influences of early domestication of large herds of female horses, is intermediate in length between dog and human, and there is long-range haplotype sharing among breeds.

Horse pancreatic lipase-related proteins PLRP1 and PLRP2 are produced by the pancreas together with pancreatic lipase (PL). Sequence-comparison analyses reveal that the three proteins possess the same two-domain organization: an N-terminal catalytic domain and a C-terminal domain, which in PL is involved in colipase binding. Nevertheless, despite the high level of sequence identity found, they exhibit distinct enzymatic properties. The intrinsic sensitivity of the peptide bond between Ser245 and Thr246 within the flap region of PLRP2 to proteolytic cleavage probably complicates PLRP2 crystallization since, as shown here, this proteolyzed form of PLRP2 is only crystallized after specific detergent stabilization of this region. This has been performed by the hanging-drop vapour-diffusion method at 291 K and exclusively in the presence of N,N-dimethyldecylamine-beta-oxide (DDAO). However, most crystals (>95%) are highly twinned and diffract poorly (to approximately 7-5 A resolution). Diffraction-quality trigonal crystals have unit-cell parameters a = b = 128.4, c = 85.8 A and belong to space group P3(2)21. A 2.9 A native data set was collected at ESRF on beamline ID14-2 with an R(merge) of 12.7%. Preliminary structural analysis provides a structural basis for the specific roles of DDAO.

Although structurally similar to pancreatic lipase (PL), the key enzyme of intestinal fat digestion, pancreatic lipase-related protein type 2 (PLRP2) differs from PL in certain functional properties. Notably, PLRP2 has a broader substrate specificity than PL, and unlike that of PL, its activity is not restored by colipase in the presence of bile salts. In the studies presented here, the activation mechanism of horse PLRP2 was studied through active site-directed inhibition experiments, and the results demonstrate fundamental differences with that of PL. The opening of the horse PLRP2 flap occurs as soon as bile salt monomers are present, is accelerated in the presence of micelles, and does not require the presence of colipase. Moreover, in contrast to PL, horse PLRP2 is able to directly interact with a bile salt micelle to form an active binary complex, without the micelle being presented by colipase, as evidenced by molecular sieving experiments. These findings, together with the sensitivity of the horse PLRP2 flap to partial proteolysis, are indicative of a higher flexibility of the flap of horse PLRP2 relative to PL. From these results, it can be concluded that PLRP2 can adopt an active conformation in the intestine, which could be important for the further understanding of the physiological role of PLRP2. Finally, this work emphasizes the essential role of colipase in lipase catalysis at the lipid-water interface in the presence of bile.