diff --git a/sa-index/Cargo.toml b/sa-index/Cargo.toml
index de57fc9..cf2d524 100644
--- a/sa-index/Cargo.toml
+++ b/sa-index/Cargo.toml
@@ -16,3 +16,4 @@ serde = { version = "1.0.197", features = ["derive"] }
 sa-mappings = { path = "../sa-mappings" }
 bitarray = { path = "../bitarray" }
 serde_json = "1.0.116"
+vers-vecs = "1.5.0"
diff --git a/sa-index/src/sa_searcher.rs b/sa-index/src/sa_searcher.rs
index e00d216..757c7b8 100644
--- a/sa-index/src/sa_searcher.rs
+++ b/sa-index/src/sa_searcher.rs
@@ -8,6 +8,7 @@ use crate::{
     Nullable, SuffixArray
 };
 use crate::bounds_cache::BoundsCache;
+use crate::suffix_to_protein_index::RankSuffixToProtein;
 
 /// Enum indicating if we are searching for the minimum, or maximum bound in the suffix array
 #[derive(Clone, Copy, PartialEq)]
@@ -108,6 +109,24 @@ impl Deref for DenseSearcher {
     }
 }
 
+pub struct RankSearcher(Searcher);
+
+impl RankSearcher {
+    pub fn new(sa: SuffixArray, proteins: Proteins, k: usize) -> Self {
+        let suffix_index_to_protein = RankSuffixToProtein::new(&proteins.input_string);
+        let searcher = Searcher::new(sa, proteins, Box::new(suffix_index_to_protein), k);
+        Self(searcher)
+    }
+}
+
+impl Deref for RankSearcher {
+    type Target = Searcher;
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
 /// Struct that contains all the elements needed to search a peptide in the suffix array
 /// This struct also contains all the functions used for search
 ///
diff --git a/sa-index/src/suffix_to_protein_index.rs b/sa-index/src/suffix_to_protein_index.rs
index 121b569..743fc24 100644
--- a/sa-index/src/suffix_to_protein_index.rs
+++ b/sa-index/src/suffix_to_protein_index.rs
@@ -1,4 +1,5 @@
 use clap::ValueEnum;
+use vers_vecs::{BitVec, RsVec};
 use sa_mappings::proteins::{SEPARATION_CHARACTER, TERMINATION_CHARACTER};
 
 use crate::Nullable;
@@ -38,6 +39,10 @@ pub struct SparseSuffixToProtein {
     mapping: Vec<i64>
 }
 
+pub struct RankSuffixToProtein {
+    mapping: RsVec
+}
+
 impl SuffixToProteinIndex for DenseSuffixToProtein {
     fn suffix_to_protein(&self, suffix: i64) -> u32 {
         self.mapping[suffix as usize]
@@ -57,6 +62,16 @@ impl SuffixToProteinIndex for SparseSuffixToProtein {
     }
 }
 
+impl SuffixToProteinIndex for RankSuffixToProtein {
+    fn suffix_to_protein(&self, suffix: i64) -> u32 {
+        if let Some(1) = self.mapping.get(suffix as usize) {
+            return u32::NULL;
+        }
+
+        self.mapping.rank1(suffix as usize) as u32
+    }
+}
+
 impl DenseSuffixToProtein {
     /// Creates a new DenseSuffixToProtein mapping
     ///
@@ -104,6 +119,21 @@ impl SparseSuffixToProtein {
     }
 }
 
+impl RankSuffixToProtein {
+    pub fn new(text: &[u8]) -> Self {
+        let mut bit_vector = BitVec::from_zeros(text.len());
+        for (index, &char) in text.iter().enumerate() {
+            if char == SEPARATION_CHARACTER || char == TERMINATION_CHARACTER {
+                bit_vector.set(index, 1).unwrap();
+            }
+        }
+
+        Self {
+            mapping: RsVec::from_bit_vec(bit_vector)
+        }
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use clap::ValueEnum;
@@ -115,6 +145,7 @@ mod tests {
         },
         Nullable
     };
+    use crate::suffix_to_protein_index::RankSuffixToProtein;
 
     fn build_text() -> Vec<u8> {
         let mut text = ["ACG", "CG", "AAA"].join(&format!("{}", SEPARATION_CHARACTER as char));
@@ -172,4 +203,16 @@ mod tests {
         // suffix that starts with TERMINATION_CHARACTER
         assert_eq!(index.suffix_to_protein(10), u32::NULL);
     }
+
+    #[test]
+    fn test_search_rank() {
+        let u8_text = &build_text();
+        let index = RankSuffixToProtein::new(u8_text);
+        assert_eq!(index.suffix_to_protein(5), 1);
+        assert_eq!(index.suffix_to_protein(7), 2);
+        // suffix that starts with SEPARATION_CHARACTER
+        assert_eq!(index.suffix_to_protein(3), u32::NULL);
+        // suffix that starts with TERMINATION_CHARACTER
+        assert_eq!(index.suffix_to_protein(10), u32::NULL);
+    }
 }