Besides hemoglobin, what proteins are present in red blood cells?

Question

I knew that mature red blood cells (RBCs) lacked nuclei, but I wasn't aware until just now that they also lacked ribosomes and mitochondria. Most cells in the human body all contain a common laundry list of housekeeping proteins and RNAs (including mitochondrial proteins and ribosomal RNAs), but I guess RBCs lack a number of them. Do they still have all of the other organelles? Obviously hemoglobin (and to a lesser extent carbonic anhydrase) makes up a large portion of the dry weight of RBCs, but are other proteins still present? If so, what are their relative abundances?

For example, do red blood cells have any of the normal metabolic (i.e. ATP producing) proteins? Obviously they don't have any of the TCA cycle proteins, but do they still have the glycolysis ones?

Answer 1

Reticulocyte stage is when the ribosomes are still present and after that no new protein synthesis occurs. However RBCs have a lot of proteins and major proteins other than haemoglobin are cytoskeletal proteins and ion channels/pumps (In fact, cytoskeletal proteins are more abundant than haemoglobin). It is the Na⁺-K⁺-ATPase that consumes most ATP. As you correctly identified the RBCs produce ATP via glycolysis and glycolytic enzymes are also present. Note that deficiency of pyruvate kinase leads to haemolytic anaemia.

For a detail on the proteins present in human RBSs, see this paper. They have studied the RBC proteome by ion-trap MS. The top 5 proteins (from Table-1) are:

No.    Protein description              Molecular mass (Da)    Gi Number    Sequence     No. of identified 
                                                                           coverage(%)      peptides 
1      Spectrin α chain, erythrocyte         279,916.5          1174412       48.0           77*
2      Spectrin β chain, erythrocyte         246,468.1          17476989      48.0           76*
3      Ankyrin 1, splice form 2              206,067.9          105337        45.0           55
4      Ankyrin 1, isoform 4, erythrocytic    203,416.6          10947036      45.0           50
5      Ankyrin 1, isoform 2, erythrocytic    189,011.2          10947042      46.0           48

Although in this table you cannot find glycolytic enzymes other than GAPDH and Aldolase, but other enzymes are also present. They are perhaps not detected in this experiment because of overwhelming levels of structural proteins. You can check this old paper that shows a study of different glycolytic enzymes from erythrocytes. It is also to be noted that the glycolytic pathway flux is not as smooth as in other cells. So some accumulated metabolites are probably exported out of the cells to keep the flux smooth^{[ref Full text not found]}.