Carriers of hemoglobin Providence have three types of β chain in their hemolysates. The two abnormal chains have asparagine (Providence N, Prov N) or aspartic acid (Providence D) at position β 82, instead of lysine. In vitro, only two β chains are synthesized by reticulocytes of carriers, β(A) and β(provN). In vivo studies showed that the specific activity of Providence N was initially 10 fold higher than that of Providence D; the specific activities of the two labeled hemoglobins were approximately equal 5 wk after injection of isotope. Oxygen affinity of carriers' blood was somewhat increased, but they were not polycythemic. The affinity of the purified hemoglobins Providence was decreased. Addition of 2, 3 diphosphoglycerate had little effect on the affinity of either hemoglobin component, and addition of inositol hexaphosphate produced no change in the affinity of Providence D. These studies demonstrate that Providence N is deamidated to Providence D during the life span of the erythrocyte, and suggest this finding may represent only an easily observed prototype of posttranslational modification of proteins in general. Despite an abnormal P50 of the blood, oxygen transport is probably normal in carriers of the abnormal hemoglobins.
ASJC Scopus subject areas