ABSTRACT
As the main carrier of oxygen delivery in the blood circulation system, hemoglobin (Hb) plays a key role in the adaptation of animals to high altitude hypoxia.In this paper, we combined analysis of genome, transcriptome, molecular evolution, homology modeling and molecular dynamics simulation, and explored the molecular mechanisms of increased blood oxygen affinity of Pseudopodoces humilis.Our results showed that the prenatal expressed p gene was highly expressed in the adult Pseudopodoces humilis (RPKM = 32.22) compared to Parus major (RPKM = 0), and this may result in the presence of two additional p-type Hbs with high oxygen affinity in the blood of P.humilis, i.e.(al>p)2 and (aAp)2.The PA25G-A and pA55L-I mutations may increase the van der Waals force between the B and D helices, which might eventually make the entire Pv subunit more compact and finally reduce the number of hydrogen bonds between a dimers, hence the transition from T state to R state is prone to occur.The two mutations of (3a43A-S and pA44S-N could change the conformation and polarity of the heme pocket opening, thus making the solution easier to flow into/out of the heme pocket and therefore facilitating the gas exchange.The pA90E-K mutation in P.humilis has undergone strong positive selection, which could increase the basicity of pA-type Hb, thereby offsetting the decrease in Hb-02 affinity caused by the Bohr effect.In addition, we also found that aA44P-S and pA43A-S mutations may increase the hydrophilicity of otA and pv type Hbs, which is beneficial to the accumulation of Hb to a higher concentration in red blood cells.Collectively, the prenatal Hb genes highly expressed in the adult together with the genetic based changes in intrinsic 0, affinity and physicochemical property of aA and pA Hb could be the main causes for the increase in blood oxygen affinity of P.humilus.
ABSTRACT
The complete sequence of Pseudopodoces humilis mitochondrial genome was determined by using L-PCR and conserved primer walking approaches. The results showed that the entire mitochondrial genome of P. humilis was 16,758 bp in length with 52.5% A + T content; the genome harbored the same gene order with that of other birds, including 2 rRNA genes, 13 protein-coding genes, 22 tRNA genes and 1 non-coding control region. All tRNAs formed typical cloverleaf secondary structures (excluding tRNASer-AGN). The control region (D-loop) of P. humilis was located between tRNAGlu and tRNAPhe with 1168 bp length, no repetitive sequence.
